diff --git a/doc/examples/box2d/contact_callbacks/lib/boundaries.dart b/doc/examples/box2d/contact_callbacks/lib/boundaries.dart
index 4dce6fb59..91658d1c5 100644
--- a/doc/examples/box2d/contact_callbacks/lib/boundaries.dart
+++ b/doc/examples/box2d/contact_callbacks/lib/boundaries.dart
@@ -27,9 +27,7 @@ class Wall extends BodyComponent {
   final Vector2 start;
   final Vector2 end;
 
-  Wall(this.start, this.end, Box2DGame game) : super(game) {
-    _createBody(start, end);
-  }
+  Wall(this.start, this.end, Box2DGame game) : super(game);
 
   @override
   void renderPolygon(Canvas canvas, List<Offset> coordinates) {
@@ -38,7 +36,8 @@ class Wall extends BodyComponent {
     canvas.drawLine(start, end, paint);
   }
 
-  void _createBody(Vector2 start, Vector2 end) {
+  @override
+  Body createBody() {
     final PolygonShape shape = PolygonShape();
     shape.setAsEdge(start, end);
 
@@ -52,6 +51,6 @@ class Wall extends BodyComponent {
       ..position = Vector2.zero()
       ..type = BodyType.STATIC;
 
-    body = world.createBody(bodyDef)..createFixtureFromFixtureDef(fixtureDef);
+    return world.createBody(bodyDef)..createFixtureFromFixtureDef(fixtureDef);
   }
 }
diff --git a/doc/examples/box2d/contact_callbacks/lib/main.dart b/doc/examples/box2d/contact_callbacks/lib/main.dart
index 13b42a32b..f25fc5777 100644
--- a/doc/examples/box2d/contact_callbacks/lib/main.dart
+++ b/doc/examples/box2d/contact_callbacks/lib/main.dart
@@ -19,12 +19,13 @@ void main() async {
 class Ball extends BodyComponent {
   Paint originalPaint, currentPaint;
   bool giveNudge = false;
+  final double _radius = 5.0;
+  Vector2 _position;
 
   Ball(Vector2 position, Box2DGame box2d) : super(box2d) {
     originalPaint = _randomPaint();
     currentPaint = originalPaint;
-    final worldPosition = viewport.getScreenToWorld(position);
-    _createBody(5.0, worldPosition);
+    _position = viewport.getScreenToWorld(position);
   }
 
   Paint _randomPaint() {
@@ -39,9 +40,10 @@ class Ball extends BodyComponent {
     ).paint;
   }
 
-  void _createBody(double radius, Vector2 position) {
+  @override
+  Body createBody() {
     final CircleShape shape = CircleShape();
-    shape.radius = radius;
+    shape.radius = _radius;
 
     final fixtureDef = FixtureDef()
       ..shape = shape
@@ -52,10 +54,10 @@ class Ball extends BodyComponent {
     final bodyDef = BodyDef()
       // To be able to determine object in collision
       ..setUserData(this)
-      ..position = position
+      ..position = _position
       ..type = BodyType.DYNAMIC;
 
-    body = world.createBody(bodyDef)..createFixtureFromFixtureDef(fixtureDef);
+    return world.createBody(bodyDef)..createFixtureFromFixtureDef(fixtureDef);
   }
 
   @override
diff --git a/doc/examples/box2d/simple/lib/main.dart b/doc/examples/box2d/simple/lib/main.dart
index 756b01faa..70e74d7e6 100644
--- a/doc/examples/box2d/simple/lib/main.dart
+++ b/doc/examples/box2d/simple/lib/main.dart
@@ -23,13 +23,12 @@ class MyPlanet extends BodyComponent {
   // components that are added to the same Box2DGame/Box2DComponent.
   // After 20 seconds the circle will be removed, to show that we don't get
   // any concurrent modification exceptions.
-  MyPlanet(Box2DGame game) : super(game) {
-    _createBody(50.0, Vector2.zero());
-  }
+  MyPlanet(Box2DGame game) : super(game);
 
-  void _createBody(double radius, Vector2 position) {
+  @override
+  Body createBody() {
     final CircleShape shape = CircleShape();
-    shape.radius = radius;
+    shape.radius = 50.0;
 
     final fixtureDef = FixtureDef();
     // To be able to determine object in collision
@@ -40,11 +39,11 @@ class MyPlanet extends BodyComponent {
     fixtureDef.friction = 0.1;
 
     final bodyDef = BodyDef();
-    bodyDef.position = position;
+    bodyDef.position = Vector2.zero();
     bodyDef.angularVelocity = 4.0;
     bodyDef.type = BodyType.DYNAMIC;
 
-    body = world.createBody(bodyDef)..createFixtureFromFixtureDef(fixtureDef);
+    return world.createBody(bodyDef)..createFixtureFromFixtureDef(fixtureDef);
   }
 
   @override