diff --git a/core/src/avm2/activation.rs b/core/src/avm2/activation.rs
index 69f19cf58e67..b13b5b3439b4 100644
--- a/core/src/avm2/activation.rs
+++ b/core/src/avm2/activation.rs
@@ -334,9 +334,7 @@ impl<'a, 'gc> Activation<'a, 'gc> {
         {
             let string_callee = istr!(self, "callee");
 
-            args_object
-                .set_string_property_local(string_callee, callee, self)
-                .unwrap();
+            args_object.set_dynamic_property(string_callee, callee, self.gc());
             args_object.set_local_property_is_enumerable(self.gc(), string_callee, false);
         }
 
@@ -1811,7 +1809,7 @@ impl<'a, 'gc> Activation<'a, 'gc> {
             let value = self.pop_stack();
             let name = self.pop_stack();
 
-            object.set_string_property_local(name.coerce_to_string(self)?, value, self)?;
+            object.set_dynamic_property(name.coerce_to_string(self)?, value, self.gc());
         }
 
         self.push_stack(object);
diff --git a/core/src/avm2/amf.rs b/core/src/avm2/amf.rs
index 174ab508b993..3223aac9f859 100644
--- a/core/src/avm2/amf.rs
+++ b/core/src/avm2/amf.rs
@@ -313,11 +313,20 @@ pub fn deserialize_value_impl<'gc>(
 
             // Now let's add each element as a property
             for element in elements {
-                array.set_string_property_local(
-                    AvmString::new_utf8(activation.gc(), element.name()),
-                    deserialize_value_impl(activation, element.value(), object_map)?,
-                    activation,
-                )?;
+                let name = ruffle_wstr::from_utf8(element.name());
+                let value = deserialize_value_impl(activation, element.value(), object_map)?;
+
+                // If the name of the element was a valid array index, we set an
+                // element on the array instead of setting a dynamic property.
+                if let Some(index) = ArrayObject::as_array_index(&name) {
+                    array.set_element(activation.gc(), index, value);
+                } else {
+                    array.set_dynamic_property(
+                        AvmString::new(activation.gc(), name),
+                        value,
+                        activation.gc(),
+                    );
+                }
             }
             array.into()
         }
@@ -462,7 +471,7 @@ pub fn deserialize_value_impl<'gc>(
                     dict_obj.set_property_by_object(key, value, activation.gc());
                 } else {
                     let key_string = key.coerce_to_string(activation)?;
-                    dict_obj.set_string_property_local(key_string, value, activation)?;
+                    dict_obj.set_dynamic_property(key_string, value, activation.gc());
                 }
             }
             dict_obj.into()
@@ -499,11 +508,11 @@ pub fn deserialize_lso<'gc>(
     let obj = ScriptObject::new_object(activation);
 
     for child in &lso.body {
-        obj.set_string_property_local(
+        obj.set_dynamic_property(
             AvmString::new_utf8(activation.gc(), &child.name),
             deserialize_value(activation, child.value())?,
-            activation,
-        )?;
+            activation.gc(),
+        );
     }
 
     Ok(obj)
diff --git a/core/src/avm2/flv.rs b/core/src/avm2/flv.rs
index a220a6314bab..fd661e361048 100644
--- a/core/src/avm2/flv.rs
+++ b/core/src/avm2/flv.rs
@@ -15,13 +15,11 @@ fn avm2_object_from_flv_variables<'gc>(
     for value in variables {
         let property_name = value.name;
 
-        info_object
-            .set_string_property_local(
-                AvmString::new_utf8_bytes(activation.gc(), property_name),
-                value.data.to_avm2_value(activation),
-                activation,
-            )
-            .expect("valid set");
+        info_object.set_dynamic_property(
+            AvmString::new_utf8_bytes(activation.gc(), property_name),
+            value.data.to_avm2_value(activation),
+            activation.gc(),
+        );
     }
 
     info_object.into()
diff --git a/core/src/avm2/globals/avmplus.rs b/core/src/avm2/globals/avmplus.rs
index 6640a9502239..80cb00ecec76 100644
--- a/core/src/avm2/globals/avmplus.rs
+++ b/core/src/avm2/globals/avmplus.rs
@@ -38,33 +38,33 @@ pub fn describe_type_json<'gc>(
         .dollar_removed_name(activation.gc())
         .to_qualified_name(activation.gc());
 
-    object.set_string_property_local(istr!("name"), qualified_name.into(), activation)?;
+    object.set_dynamic_property(istr!("name"), qualified_name.into(), activation.gc());
 
-    object.set_string_property_local(
+    object.set_dynamic_property(
         istr!("isDynamic"),
         (!used_class_def.is_sealed()).into(),
-        activation,
-    )?;
-    object.set_string_property_local(
+        activation.gc(),
+    );
+    object.set_dynamic_property(
         istr!("isFinal"),
         used_class_def.is_final().into(),
-        activation,
-    )?;
-    object.set_string_property_local(
+        activation.gc(),
+    );
+    object.set_dynamic_property(
         istr!("isStatic"),
         value
             .as_object()
             .and_then(|o| o.as_class_object())
             .is_some()
             .into(),
-        activation,
-    )?;
+        activation.gc(),
+    );
 
-    let traits = describe_internal_body(activation, used_class_def, flags)?;
+    let traits = describe_internal_body(activation, used_class_def, flags);
     if flags.contains(DescribeTypeFlags::INCLUDE_TRAITS) {
-        object.set_string_property_local(istr!("traits"), traits.into(), activation)?;
+        object.set_dynamic_property(istr!("traits"), traits.into(), activation.gc());
     } else {
-        object.set_string_property_local(istr!("traits"), Value::Null, activation)?;
+        object.set_dynamic_property(istr!("traits"), Value::Null, activation.gc());
     }
 
     Ok(object.into())
@@ -91,7 +91,7 @@ fn describe_internal_body<'gc>(
     activation: &mut Activation<'_, 'gc>,
     class_def: Class<'gc>,
     flags: DescribeTypeFlags,
-) -> Result<Object<'gc>, Error<'gc>> {
+) -> Object<'gc> {
     let mc = activation.gc();
 
     let traits = ScriptObject::new_object(activation);
@@ -103,33 +103,33 @@ fn describe_internal_body<'gc>(
     let methods = ArrayObject::empty(activation);
 
     if flags.contains(DescribeTypeFlags::INCLUDE_BASES) {
-        traits.set_string_property_local(istr!("bases"), bases.into(), activation)?;
+        traits.set_dynamic_property(istr!("bases"), bases.into(), activation.gc());
     } else {
-        traits.set_string_property_local(istr!("bases"), Value::Null, activation)?;
+        traits.set_dynamic_property(istr!("bases"), Value::Null, activation.gc());
     }
 
     if flags.contains(DescribeTypeFlags::INCLUDE_INTERFACES) {
-        traits.set_string_property_local(istr!("interfaces"), interfaces.into(), activation)?;
+        traits.set_dynamic_property(istr!("interfaces"), interfaces.into(), activation.gc());
     } else {
-        traits.set_string_property_local(istr!("interfaces"), Value::Null, activation)?;
+        traits.set_dynamic_property(istr!("interfaces"), Value::Null, activation.gc());
     }
 
     if flags.contains(DescribeTypeFlags::INCLUDE_VARIABLES) {
-        traits.set_string_property_local(istr!("variables"), variables.into(), activation)?;
+        traits.set_dynamic_property(istr!("variables"), variables.into(), activation.gc());
     } else {
-        traits.set_string_property_local(istr!("variables"), Value::Null, activation)?;
+        traits.set_dynamic_property(istr!("variables"), Value::Null, activation.gc());
     }
 
     if flags.contains(DescribeTypeFlags::INCLUDE_ACCESSORS) {
-        traits.set_string_property_local(istr!("accessors"), accessors.into(), activation)?;
+        traits.set_dynamic_property(istr!("accessors"), accessors.into(), activation.gc());
     } else {
-        traits.set_string_property_local(istr!("accessors"), Value::Null, activation)?;
+        traits.set_dynamic_property(istr!("accessors"), Value::Null, activation.gc());
     }
 
     if flags.contains(DescribeTypeFlags::INCLUDE_METHODS) {
-        traits.set_string_property_local(istr!("methods"), methods.into(), activation)?;
+        traits.set_dynamic_property(istr!("methods"), methods.into(), activation.gc());
     } else {
-        traits.set_string_property_local(istr!("methods"), Value::Null, activation)?;
+        traits.set_dynamic_property(istr!("methods"), Value::Null, activation.gc());
     }
 
     let mut bases_array = bases.array_storage_mut(mc);
@@ -214,31 +214,31 @@ fn describe_internal_body<'gc>(
                 let trait_metadata = vtable.get_metadata_for_slot(*slot_id);
 
                 let variable = ScriptObject::new_object(activation);
-                variable.set_string_property_local(istr!("name"), prop_name.into(), activation)?;
-                variable.set_string_property_local(
+                variable.set_dynamic_property(istr!("name"), prop_name.into(), activation.gc());
+                variable.set_dynamic_property(
                     istr!("type"),
                     prop_class_name.into(),
-                    activation,
-                )?;
-                variable.set_string_property_local(istr!("access"), access.into(), activation)?;
-                variable.set_string_property_local(
+                    activation.gc(),
+                );
+                variable.set_dynamic_property(istr!("access"), access.into(), activation.gc());
+                variable.set_dynamic_property(
                     istr!("uri"),
                     uri.map_or(Value::Null, |u| u.into()),
-                    activation,
-                )?;
+                    activation.gc(),
+                );
 
-                variable.set_string_property_local(istr!("metadata"), Value::Null, activation)?;
+                variable.set_dynamic_property(istr!("metadata"), Value::Null, activation.gc());
 
                 if flags.contains(DescribeTypeFlags::INCLUDE_METADATA) {
                     let metadata_object = ArrayObject::empty(activation);
                     if let Some(metadata) = trait_metadata {
-                        write_metadata(metadata_object, metadata, activation)?;
+                        write_metadata(metadata_object, metadata, activation);
                     }
-                    variable.set_string_property_local(
+                    variable.set_dynamic_property(
                         istr!("metadata"),
                         metadata_object.into(),
-                        activation,
-                    )?;
+                        activation.gc(),
+                    );
                 }
 
                 variables_array.push(variable.into());
@@ -277,47 +277,43 @@ fn describe_internal_body<'gc>(
 
                 let method_obj = ScriptObject::new_object(activation);
 
-                method_obj.set_string_property_local(
-                    istr!("name"),
-                    prop_name.into(),
-                    activation,
-                )?;
-                method_obj.set_string_property_local(
+                method_obj.set_dynamic_property(istr!("name"), prop_name.into(), activation.gc());
+                method_obj.set_dynamic_property(
                     istr!("returnType"),
                     return_type_name.into(),
-                    activation,
-                )?;
-                method_obj.set_string_property_local(
+                    activation.gc(),
+                );
+                method_obj.set_dynamic_property(
                     istr!("declaredBy"),
                     declared_by_name.into(),
-                    activation,
-                )?;
+                    activation.gc(),
+                );
 
-                method_obj.set_string_property_local(
+                method_obj.set_dynamic_property(
                     istr!("uri"),
                     uri.map_or(Value::Null, |u| u.into()),
-                    activation,
-                )?;
+                    activation.gc(),
+                );
 
-                let params = write_params(&method.method, activation)?;
-                method_obj.set_string_property_local(
+                let params = write_params(&method.method, activation);
+                method_obj.set_dynamic_property(
                     istr!("parameters"),
                     params.into(),
-                    activation,
-                )?;
+                    activation.gc(),
+                );
 
-                method_obj.set_string_property_local(istr!("metadata"), Value::Null, activation)?;
+                method_obj.set_dynamic_property(istr!("metadata"), Value::Null, activation.gc());
 
                 if flags.contains(DescribeTypeFlags::INCLUDE_METADATA) {
                     let metadata_object = ArrayObject::empty(activation);
                     if let Some(metadata) = trait_metadata {
-                        write_metadata(metadata_object, metadata, activation)?;
+                        write_metadata(metadata_object, metadata, activation);
                     }
-                    method_obj.set_string_property_local(
+                    method_obj.set_dynamic_property(
                         istr!("metadata"),
                         metadata_object.into(),
-                        activation,
-                    )?;
+                        activation.gc(),
+                    );
                 }
                 methods_array.push(method_obj.into());
             }
@@ -362,60 +358,52 @@ fn describe_internal_body<'gc>(
                 let declared_by = defining_class.dollar_removed_name(mc).to_qualified_name(mc);
 
                 let accessor_obj = ScriptObject::new_object(activation);
-                accessor_obj.set_string_property_local(
-                    istr!("name"),
-                    prop_name.into(),
-                    activation,
-                )?;
-                accessor_obj.set_string_property_local(
-                    istr!("access"),
-                    access.into(),
-                    activation,
-                )?;
-                accessor_obj.set_string_property_local(
+                accessor_obj.set_dynamic_property(istr!("name"), prop_name.into(), activation.gc());
+                accessor_obj.set_dynamic_property(istr!("access"), access.into(), activation.gc());
+                accessor_obj.set_dynamic_property(
                     istr!("type"),
                     accessor_type.into(),
-                    activation,
-                )?;
-                accessor_obj.set_string_property_local(
+                    activation.gc(),
+                );
+                accessor_obj.set_dynamic_property(
                     istr!("declaredBy"),
                     declared_by.into(),
-                    activation,
-                )?;
-                accessor_obj.set_string_property_local(
+                    activation.gc(),
+                );
+                accessor_obj.set_dynamic_property(
                     istr!("uri"),
                     uri.map_or(Value::Null, |u| u.into()),
-                    activation,
-                )?;
+                    activation.gc(),
+                );
 
                 let metadata_object = ArrayObject::empty(activation);
 
                 if let Some(get_disp_id) = get {
                     if let Some(metadata) = vtable.get_metadata_for_disp(*get_disp_id) {
-                        write_metadata(metadata_object, metadata, activation)?;
+                        write_metadata(metadata_object, metadata, activation);
                     }
                 }
 
                 if let Some(set_disp_id) = set {
                     if let Some(metadata) = vtable.get_metadata_for_disp(*set_disp_id) {
-                        write_metadata(metadata_object, metadata, activation)?;
+                        write_metadata(metadata_object, metadata, activation);
                     }
                 }
 
                 if flags.contains(DescribeTypeFlags::INCLUDE_METADATA)
                     && metadata_object.array_storage().length() > 0
                 {
-                    accessor_obj.set_string_property_local(
+                    accessor_obj.set_dynamic_property(
                         istr!("metadata"),
                         metadata_object.into(),
-                        activation,
-                    )?;
+                        activation.gc(),
+                    );
                 } else {
-                    accessor_obj.set_string_property_local(
+                    accessor_obj.set_dynamic_property(
                         istr!("metadata"),
                         Value::Null,
-                        activation,
-                    )?;
+                        activation.gc(),
+                    );
                 }
 
                 accessors_array.push(accessor_obj.into());
@@ -428,11 +416,11 @@ fn describe_internal_body<'gc>(
     if let Some(constructor) = constructor.filter(|c| {
         !c.signature().is_empty() && flags.contains(DescribeTypeFlags::INCLUDE_CONSTRUCTOR)
     }) {
-        let params = write_params(&constructor, activation)?;
-        traits.set_string_property_local(istr!("constructor"), params.into(), activation)?;
+        let params = write_params(&constructor, activation);
+        traits.set_dynamic_property(istr!("constructor"), params.into(), activation.gc());
     } else {
         // This is needed to override the normal 'constructor' property
-        traits.set_string_property_local(istr!("constructor"), Value::Null, activation)?;
+        traits.set_dynamic_property(istr!("constructor"), Value::Null, activation.gc());
     }
 
     if flags.contains(DescribeTypeFlags::INCLUDE_METADATA) {
@@ -444,12 +432,12 @@ fn describe_internal_body<'gc>(
         );
 
         let metadata_object = ArrayObject::empty(activation);
-        traits.set_string_property_local(istr!("metadata"), metadata_object.into(), activation)?;
+        traits.set_dynamic_property(istr!("metadata"), metadata_object.into(), activation.gc());
     } else {
-        traits.set_string_property_local(istr!("metadata"), Value::Null, activation)?;
+        traits.set_dynamic_property(istr!("metadata"), Value::Null, activation.gc());
     }
 
-    Ok(traits)
+    traits
 }
 
 fn display_name<'gc>(
@@ -466,31 +454,30 @@ fn display_name<'gc>(
 fn write_params<'gc>(
     method: &Method<'gc>,
     activation: &mut Activation<'_, 'gc>,
-) -> Result<ArrayObject<'gc>, Error<'gc>> {
+) -> ArrayObject<'gc> {
     let params = ArrayObject::empty(activation);
     let mut params_array = params.array_storage_mut(activation.gc());
     for param in method.signature() {
         let param_type_name = display_name(activation.strings(), param.param_type_name);
         let optional = param.default_value.is_some();
         let param_obj = ScriptObject::new_object(activation);
-        param_obj.set_string_property_local(istr!("type"), param_type_name.into(), activation)?;
-        param_obj.set_string_property_local(istr!("optional"), optional.into(), activation)?;
+        param_obj.set_dynamic_property(istr!("type"), param_type_name.into(), activation.gc());
+        param_obj.set_dynamic_property(istr!("optional"), optional.into(), activation.gc());
         params_array.push(param_obj.into());
     }
-    Ok(params)
+    params
 }
 
 fn write_metadata<'gc>(
     metadata_object: ArrayObject<'gc>,
     trait_metadata: &[Metadata<'gc>],
     activation: &mut Activation<'_, 'gc>,
-) -> Result<(), Error<'gc>> {
+) {
     let mut metadata_array = metadata_object.array_storage_mut(activation.gc());
 
     for single_trait in trait_metadata.iter() {
-        metadata_array.push(single_trait.as_json_object(activation)?.into());
+        metadata_array.push(single_trait.as_json_object(activation).into());
     }
-    Ok(())
 }
 
 /// Like `Value::instance_class`, but supports Value::Null and Value::Undefined,
diff --git a/core/src/avm2/globals/flash/display/loader_info.rs b/core/src/avm2/globals/flash/display/loader_info.rs
index a6d088f648a2..0722ea1b6226 100644
--- a/core/src/avm2/globals/flash/display/loader_info.rs
+++ b/core/src/avm2/globals/flash/display/loader_info.rs
@@ -554,7 +554,7 @@ pub fn get_parameters<'gc>(
         for (k, v) in parameters.iter() {
             let avm_k = AvmString::new_utf8(activation.gc(), k);
             let avm_v = AvmString::new_utf8(activation.gc(), v);
-            params_obj.set_string_property_local(avm_k, avm_v.into(), activation)?;
+            params_obj.set_dynamic_property(avm_k, avm_v.into(), activation.gc());
         }
 
         return Ok(params_obj.into());
diff --git a/core/src/avm2/globals/flash/display/shader_data.rs b/core/src/avm2/globals/flash/display/shader_data.rs
index 011eedd3d468..bec0d516ba45 100644
--- a/core/src/avm2/globals/flash/display/shader_data.rs
+++ b/core/src/avm2/globals/flash/display/shader_data.rs
@@ -32,13 +32,13 @@ pub fn init<'gc>(
         // Top-level metadata appears to turn `TInt` into a plain integer value,
         // rather than a single-element array.
         let value = meta.value.as_avm2_value(activation, true)?;
-        this.set_string_property_local(name, value, activation)?;
+        this.set_dynamic_property(name, value, activation.gc());
     }
-    this.set_string_property_local(
+    this.set_dynamic_property(
         istr!("name"),
         AvmString::new_utf8(activation.gc(), &shader.name).into(),
-        activation,
-    )?;
+        activation.gc(),
+    );
 
     let mut normal_index = 0;
     let mut texture_index = 0;
@@ -66,7 +66,7 @@ pub fn init<'gc>(
 
         let name = AvmString::new_utf8(activation.gc(), name);
         let param_obj = make_shader_parameter(activation, param, index)?;
-        this.set_string_property_local(name, param_obj, activation)?;
+        this.set_dynamic_property(name, param_obj, activation.gc());
     }
 
     let shader_handle = activation
diff --git a/core/src/avm2/globals/flash/display/shader_job.rs b/core/src/avm2/globals/flash/display/shader_job.rs
index aeb244e9b730..5e8f2ecf6af3 100644
--- a/core/src/avm2/globals/flash/display/shader_job.rs
+++ b/core/src/avm2/globals/flash/display/shader_job.rs
@@ -70,10 +70,7 @@ pub fn get_shader_args<'gc>(
                         });
                     }
                     let shader_param = shader_data
-                        .get_string_property_local(
-                            AvmString::new_utf8(activation.gc(), name),
-                            activation,
-                        )
+                        .get_dynamic_property(AvmString::new_utf8(activation.gc(), name))
                         .expect("Missing normal property");
 
                     let shader_param = shader_param
@@ -104,10 +101,7 @@ pub fn get_shader_args<'gc>(
                     name,
                 } => {
                     let shader_input = shader_data
-                        .get_string_property_local(
-                            AvmString::new_utf8(activation.gc(), name),
-                            activation,
-                        )
+                        .get_dynamic_property(AvmString::new_utf8(activation.gc(), name))
                         .expect("Missing property")
                         .as_object()
                         .expect("Shader input is not an object");
diff --git a/core/src/avm2/globals/flash/display/shader_parameter.rs b/core/src/avm2/globals/flash/display/shader_parameter.rs
index 3f2deb3b0761..50de6509fc8b 100644
--- a/core/src/avm2/globals/flash/display/shader_parameter.rs
+++ b/core/src/avm2/globals/flash/display/shader_parameter.rs
@@ -43,11 +43,11 @@ pub fn make_shader_parameter<'gc>(
                     param_object.set_slot(parameter_slots::_VALUE, value, activation)?;
                 }
             }
-            param_object.set_string_property_local(
+            param_object.set_dynamic_property(
                 istr!("name"),
                 AvmString::new_utf8(activation.gc(), name).into(),
-                activation,
-            )?;
+                activation.gc(),
+            );
             Ok(param_value)
         }
         PixelBenderParam::Texture { name, channels, .. } => {
@@ -61,11 +61,11 @@ pub fn make_shader_parameter<'gc>(
 
             obj.set_slot(input_slots::_CHANNELS, (*channels).into(), activation)?;
             obj.set_slot(input_slots::_INDEX, index.into(), activation)?;
-            obj.set_string_property_local(
+            obj.set_dynamic_property(
                 istr!("name"),
                 AvmString::new_utf8(activation.gc(), name).into(),
-                activation,
-            )?;
+                activation.gc(),
+            );
             Ok(obj.into())
         }
     }
diff --git a/core/src/avm2/globals/flash/text/style_sheet.rs b/core/src/avm2/globals/flash/text/style_sheet.rs
index 85be408ea17d..49600800280e 100644
--- a/core/src/avm2/globals/flash/text/style_sheet.rs
+++ b/core/src/avm2/globals/flash/text/style_sheet.rs
@@ -20,18 +20,18 @@ pub fn inner_parse_css<'gc>(
             let object = ScriptObject::new_object(activation);
 
             for (key, value) in properties.into_iter() {
-                object.set_string_property_local(
+                object.set_dynamic_property(
                     AvmString::new(activation.gc(), transform_dashes_to_camel_case(key)),
                     Value::String(AvmString::new(activation.gc(), value)),
-                    activation,
-                )?;
+                    activation.gc(),
+                );
             }
 
-            result.set_string_property_local(
+            result.set_dynamic_property(
                 AvmString::new(activation.gc(), selector),
                 Value::Object(object),
-                activation,
-            )?;
+                activation.gc(),
+            );
         }
     }
 
diff --git a/core/src/avm2/globals/json.rs b/core/src/avm2/globals/json.rs
index eaadb0c77bc8..e292f075e934 100644
--- a/core/src/avm2/globals/json.rs
+++ b/core/src/avm2/globals/json.rs
@@ -43,9 +43,9 @@ fn deserialize_json_inner<'gc>(
                     Some(reviver) => reviver.call(activation, Value::Null, &[key.into(), val])?,
                 };
                 if matches!(mapped_val, Value::Undefined) {
-                    obj.delete_string_property_local(key, activation)?;
+                    obj.delete_dynamic_property(key, activation.gc());
                 } else {
-                    obj.set_string_property_local(key, mapped_val, activation)?;
+                    obj.set_dynamic_property(key, mapped_val, activation.gc());
                 }
             }
             obj.into()
diff --git a/core/src/avm2/globals/reg_exp.rs b/core/src/avm2/globals/reg_exp.rs
index 923c9e220a2d..1be56bbf86e9 100644
--- a/core/src/avm2/globals/reg_exp.rs
+++ b/core/src/avm2/globals/reg_exp.rs
@@ -241,20 +241,20 @@ pub fn exec<'gc>(
                 |range| AvmString::new(activation.gc(), &text[range]),
             );
 
-            object.set_string_property_local(
+            object.set_dynamic_property(
                 AvmString::new_utf8(activation.gc(), name),
                 string.into(),
-                activation,
-            )?;
+                activation.gc(),
+            );
         }
 
-        object.set_string_property_local(
+        object.set_dynamic_property(
             istr!("index"),
             Value::Number(matched.start() as f64),
-            activation,
-        )?;
+            activation.gc(),
+        );
 
-        object.set_string_property_local(istr!("input"), text.into(), activation)?;
+        object.set_dynamic_property(istr!("input"), text.into(), activation.gc());
 
         return Ok(object.into());
     }
diff --git a/core/src/avm2/metadata.rs b/core/src/avm2/metadata.rs
index 19137b0d4996..dce4aefbb79e 100644
--- a/core/src/avm2/metadata.rs
+++ b/core/src/avm2/metadata.rs
@@ -74,35 +74,28 @@ impl<'gc> Metadata<'gc> {
     }
 
     // Converts the Metadata to an Object of the form used in avmplus:describeTypeJSON().
-    pub fn as_json_object(
-        &self,
-        activation: &mut Activation<'_, 'gc>,
-    ) -> Result<Object<'gc>, Error<'gc>> {
+    pub fn as_json_object(&self, activation: &mut Activation<'_, 'gc>) -> Object<'gc> {
         let object = ScriptObject::new_object(activation);
-        object.set_string_property_local(istr!("name"), self.name.into(), activation)?;
+        object.set_dynamic_property(istr!("name"), self.name.into(), activation.gc());
 
         let values = self
             .items
             .iter()
             .map(|item| {
                 let value_object = ScriptObject::new_object(activation);
-                value_object.set_string_property_local(
-                    istr!("key"),
-                    item.key.into(),
-                    activation,
-                )?;
-                value_object.set_string_property_local(
+                value_object.set_dynamic_property(istr!("key"), item.key.into(), activation.gc());
+                value_object.set_dynamic_property(
                     istr!("value"),
                     item.value.into(),
-                    activation,
-                )?;
-                Ok(Some(value_object.into()))
+                    activation.gc(),
+                );
+                Some(value_object.into())
             })
-            .collect::<Result<Vec<Option<Value<'gc>>>, Error<'gc>>>()?;
+            .collect::<Vec<Option<Value<'gc>>>>();
 
         let values_array =
             ArrayObject::from_storage(activation, ArrayStorage::from_storage(values));
-        object.set_string_property_local(istr!("value"), values_array.into(), activation)?;
-        Ok(object)
+        object.set_dynamic_property(istr!("value"), values_array.into(), activation.gc());
+        object
     }
 }
diff --git a/core/src/avm2/object.rs b/core/src/avm2/object.rs
index 38a8f43e3c66..f7cc41b46876 100644
--- a/core/src/avm2/object.rs
+++ b/core/src/avm2/object.rs
@@ -244,15 +244,22 @@ pub trait TObject<'gc>: 'gc + Collect<'gc> + Debug + Into<Object<'gc>> + Clone +
         self.base().get_property_local(name, activation)
     }
 
-    /// Same as get_property_local, but constructs a public Multiname for you.
+    /// Get a dynamic property on this Object by name. This is like
+    /// `get_property_local`, but it skips dynamic-dispatch TObject logic
+    /// and always gets a dynamic property on the base ScriptObject. If the
+    /// object is sealed, or the dynamic property does not exist on the
+    /// ScriptObject, this returns `None`.
     #[no_dynamic]
-    fn get_string_property_local(
-        self,
-        name: AvmString<'gc>,
-        activation: &mut Activation<'_, 'gc>,
-    ) -> Result<Value<'gc>, Error<'gc>> {
-        let name = Multiname::new(activation.avm2().namespaces.public_vm_internal(), name);
-        self.get_property_local(&name, activation)
+    fn get_dynamic_property(self, local_name: AvmString<'gc>) -> Option<Value<'gc>> {
+        use crate::avm2::object::script_object::maybe_int_property;
+
+        // See the comment in script_object::get_dynamic_property
+        let key = maybe_int_property(local_name);
+
+        let base = self.base();
+        let values = base.values();
+        let value = values.as_hashmap().get(&key);
+        value.map(|v| v.value)
     }
 
     /// Purely an optimization for "array-like" access. This should return
@@ -261,17 +268,6 @@ pub trait TObject<'gc>: 'gc + Collect<'gc> + Debug + Into<Object<'gc>> + Clone +
         None
     }
 
-    /// Purely an optimization for "array-like" access. This should return
-    /// `None` when the lookup needs to be forwarded to the base.
-    fn set_index_property(
-        self,
-        _activation: &mut Activation<'_, 'gc>,
-        _index: usize,
-        _value: Value<'gc>,
-    ) -> Option<Result<(), Error<'gc>>> {
-        None
-    }
-
     /// Set a local property of the object. The Multiname should always be public.
     ///
     /// This skips class field lookups and looks at:
@@ -287,19 +283,44 @@ pub trait TObject<'gc>: 'gc + Collect<'gc> + Debug + Into<Object<'gc>> + Clone +
         base.set_property_local(name, value, activation)
     }
 
-    /// Same as set_property_local, but constructs a public Multiname for you.
-    /// TODO: this feels upside down, as in: we shouldn't need multinames/namespaces
-    /// by the time we reach dynamic properties.
-    /// But for now, this function is a smaller change to the core than a full refactor.
+    /// Set a dynamic property on this Object by name. This is like
+    /// `set_property_local`, but it skips dynamic-dispatch TObject logic
+    /// and always sets a dynamic property on the base ScriptObject.
+    ///
+    /// Note that calling this method on a non-dynamic (sealed) object will
+    /// panic, as sealed objects cannot have dynamic properties set on them.
+    ///
+    /// Additionally, if the vtable of the object has the property `local_name`
+    /// in it, this method will still declare a dynamic property on the object
+    /// with the same name, so take care to only call this method on objects
+    /// that are known to not have the property `local_name` in their vtable.
     #[no_dynamic]
-    fn set_string_property_local(
+    fn set_dynamic_property(
         self,
-        name: impl Into<AvmString<'gc>>,
+        local_name: AvmString<'gc>,
         value: Value<'gc>,
-        activation: &mut Activation<'_, 'gc>,
-    ) -> Result<(), Error<'gc>> {
-        let name = Multiname::new(activation.avm2().namespaces.public_vm_internal(), name);
-        self.set_property_local(&name, value, activation)
+        mc: &Mutation<'gc>,
+    ) {
+        use crate::avm2::object::script_object::maybe_int_property;
+
+        let base = self.base();
+        assert!(!base.is_sealed());
+
+        // See the comment in ScriptObjectWrapper::set_property_local
+        let key = maybe_int_property(local_name);
+
+        base.values_mut(mc).insert(key, value);
+    }
+
+    /// Purely an optimization for "array-like" access. This should return
+    /// `None` when the lookup needs to be forwarded to the base.
+    fn set_index_property(
+        self,
+        _activation: &mut Activation<'_, 'gc>,
+        _index: usize,
+        _value: Value<'gc>,
+    ) -> Option<Result<(), Error<'gc>>> {
+        None
     }
 
     /// Init a local property of the object. The Multiname should always be public.
@@ -341,6 +362,38 @@ pub trait TObject<'gc>: 'gc + Collect<'gc> + Debug + Into<Object<'gc>> + Clone +
         result.call(activation, self_val, arguments)
     }
 
+    /// Delete a property by QName, after multiname resolution and all other
+    /// considerations have been taken.
+    ///
+    /// This required method is only intended to be called by other TObject
+    /// methods.
+    fn delete_property_local(
+        self,
+        activation: &mut Activation<'_, 'gc>,
+        name: &Multiname<'gc>,
+    ) -> Result<bool, Error<'gc>> {
+        let base = self.base();
+
+        Ok(base.delete_property_local(activation.gc(), name))
+    }
+
+    /// Delete a dynamic property on this Object by name. This is like
+    /// `delete_property_local`, but it skips dynamic-dispatch TObject logic
+    /// and always tries to delete a dynamic property on the base ScriptObject.
+    ///
+    /// This method will panic when called on a non-dynamic (sealed) object, as
+    /// sealed objects don't have dynamic properties to delete anyway.
+    #[no_dynamic]
+    fn delete_dynamic_property(self, name: AvmString<'gc>, mc: &Mutation<'gc>) {
+        use crate::avm2::object::script_object::maybe_int_property;
+
+        let base = self.base();
+        assert!(!base.is_sealed());
+
+        let key = maybe_int_property(name);
+        base.values_mut(mc).remove(&key);
+    }
+
     /// Retrieve a slot by its index.
     #[no_dynamic]
     #[inline(always)]
@@ -421,32 +474,6 @@ pub trait TObject<'gc>: 'gc + Collect<'gc> + Debug + Into<Object<'gc>> + Clone +
         self.vtable().has_trait(name)
     }
 
-    /// Delete a property by QName, after multiname resolution and all other
-    /// considerations have been taken.
-    ///
-    /// This required method is only intended to be called by other TObject
-    /// methods.
-    fn delete_property_local(
-        self,
-        activation: &mut Activation<'_, 'gc>,
-        name: &Multiname<'gc>,
-    ) -> Result<bool, Error<'gc>> {
-        let base = self.base();
-
-        Ok(base.delete_property_local(activation.gc(), name))
-    }
-
-    /// Same as delete_property_local, but constructs a public Multiname for you.
-    #[no_dynamic]
-    fn delete_string_property_local(
-        self,
-        name: impl Into<AvmString<'gc>>,
-        activation: &mut Activation<'_, 'gc>,
-    ) -> Result<bool, Error<'gc>> {
-        let name = Multiname::new(activation.avm2().namespaces.public_vm_internal(), name);
-        self.delete_property_local(activation, &name)
-    }
-
     /// Retrieve the `__proto__` of a given object.
     ///
     /// The proto is another object used to resolve methods across a class of
diff --git a/core/src/avm2/object/array_object.rs b/core/src/avm2/object/array_object.rs
index ba9dcac2b2b8..18bfb8376c32 100644
--- a/core/src/avm2/object/array_object.rs
+++ b/core/src/avm2/object/array_object.rs
@@ -7,7 +7,7 @@ use crate::avm2::object::{ClassObject, Object, ObjectPtr, TObject};
 use crate::avm2::value::Value;
 use crate::avm2::Error;
 use crate::avm2::Multiname;
-use crate::string::AvmString;
+use crate::string::{AvmString, WStr};
 use crate::utils::HasPrefixField;
 use core::fmt;
 use gc_arena::barrier::unlock;
@@ -84,7 +84,12 @@ impl<'gc> ArrayObject<'gc> {
         ))
     }
 
-    fn set_element(self, mc: &Mutation<'gc>, index: usize, value: Value<'gc>) {
+    pub fn as_array_index(local_name: &WStr) -> Option<usize> {
+        // TODO match avmplus
+        local_name.parse::<usize>().ok()
+    }
+
+    pub fn set_element(self, mc: &Mutation<'gc>, index: usize, value: Value<'gc>) {
         unlock!(Gc::write(mc, self.0), ArrayObjectData, array)
             .borrow_mut()
             .set(index, value);
@@ -115,7 +120,7 @@ impl<'gc> TObject<'gc> for ArrayObject<'gc> {
     ) -> Result<Value<'gc>, Error<'gc>> {
         if name.valid_dynamic_name() {
             if let Some(name) = name.local_name() {
-                if let Ok(index) = name.parse::<usize>() {
+                if let Some(index) = ArrayObject::as_array_index(&name) {
                     if let Some(result) = self.get_index_property(index) {
                         return Ok(result);
                     }
@@ -151,7 +156,7 @@ impl<'gc> TObject<'gc> for ArrayObject<'gc> {
 
         if name.valid_dynamic_name() {
             if let Some(name) = name.local_name() {
-                if let Ok(index) = name.parse::<usize>() {
+                if let Some(index) = ArrayObject::as_array_index(&name) {
                     self.set_element(mc, index, value);
 
                     return Ok(());
@@ -172,7 +177,7 @@ impl<'gc> TObject<'gc> for ArrayObject<'gc> {
 
         if name.valid_dynamic_name() {
             if let Some(name) = name.local_name() {
-                if let Ok(index) = name.parse::<usize>() {
+                if let Some(index) = ArrayObject::as_array_index(&name) {
                     self.set_element(mc, index, value);
 
                     return Ok(());
@@ -192,7 +197,7 @@ impl<'gc> TObject<'gc> for ArrayObject<'gc> {
 
         if name.valid_dynamic_name() {
             if let Some(name) = name.local_name() {
-                if let Ok(index) = name.parse::<usize>() {
+                if let Some(index) = ArrayObject::as_array_index(&name) {
                     unlock!(Gc::write(mc, self.0), ArrayObjectData, array)
                         .borrow_mut()
                         .delete(index);
@@ -208,7 +213,7 @@ impl<'gc> TObject<'gc> for ArrayObject<'gc> {
     fn has_own_property(self, name: &Multiname<'gc>) -> bool {
         if name.valid_dynamic_name() {
             if let Some(name) = name.local_name() {
-                if let Ok(index) = name.parse::<usize>() {
+                if let Some(index) = ArrayObject::as_array_index(&name) {
                     return self.0.array.borrow().get(index).is_some();
                 }
             }
diff --git a/core/src/avm2/object/class_object.rs b/core/src/avm2/object/class_object.rs
index 9992464791ba..426ef034e1ef 100644
--- a/core/src/avm2/object/class_object.rs
+++ b/core/src/avm2/object/class_object.rs
@@ -260,9 +260,7 @@ impl<'gc> ClassObject<'gc> {
         let mc = activation.gc();
 
         unlock!(Gc::write(mc, self.0), ClassObjectData, prototype).set(Some(class_proto));
-        class_proto
-            .set_string_property_local(istr!("constructor"), self.into(), activation)
-            .expect("Prototype is a dynamic object");
+        class_proto.set_dynamic_property(istr!("constructor"), self.into(), mc);
         class_proto.set_local_property_is_enumerable(mc, istr!("constructor"), false);
     }
 
diff --git a/core/src/avm2/object/event_object.rs b/core/src/avm2/object/event_object.rs
index 2eacc3bc06df..e94621474260 100644
--- a/core/src/avm2/object/event_object.rs
+++ b/core/src/avm2/object/event_object.rs
@@ -236,9 +236,7 @@ impl<'gc> EventObject<'gc> {
             let key = AvmString::new_utf8(activation.gc(), key);
             let value = AvmString::new_utf8(activation.gc(), value);
 
-            info_object
-                .set_string_property_local(key, Value::String(value), activation)
-                .unwrap();
+            info_object.set_dynamic_property(key, Value::String(value), activation.gc());
         }
 
         let event_name = istr!("netStatus");
diff --git a/core/src/avm2/object/script_object.rs b/core/src/avm2/object/script_object.rs
index 0173c8cd9597..636f4e1e951b 100644
--- a/core/src/avm2/object/script_object.rs
+++ b/core/src/avm2/object/script_object.rs
@@ -74,7 +74,7 @@ impl<'gc> TObject<'gc> for ScriptObject<'gc> {
     }
 }
 
-fn maybe_int_property(name: AvmString<'_>) -> DynamicKey<'_> {
+pub fn maybe_int_property(name: AvmString<'_>) -> DynamicKey<'_> {
     // TODO: this should use a custom implementation, not parse()
     // FP is much stricter here, only allowing pure natural numbers without sign or leading zeros
     if let Ok(val) = name.parse::<u32>() {
diff --git a/core/src/external.rs b/core/src/external.rs
index 55a94ade360c..0fbbe3be757f 100644
--- a/core/src/external.rs
+++ b/core/src/external.rs
@@ -248,8 +248,7 @@ impl Value {
                 for (key, value) in values.into_iter() {
                     let key = AvmString::new_utf8(activation.gc(), key);
                     let value = value.into_avm2(activation);
-                    obj.set_string_property_local(key, value, activation)
-                        .unwrap();
+                    obj.set_dynamic_property(key, value, activation.gc());
                 }
                 Avm2Value::Object(obj)
             }