Adobe Flash. AS3. Reparenting Children.

Сlicking on the car image, you can attach a trailer to it:

Below you can see my source code:
 var trailer:MovieClip = new Trailer();
    trailer.mouseEnabled = false;
    trailer.x = 120;
    trailer.y = 10;
   
var car1:MovieClip = new Car();
    car1.name = "car1";
    car1.x = 100;
    car1.y = 50;
    car1.addChild(trailer);
    addChild(car1);
   
var car2:MovieClip = new Car();
    car2.name = "car2";
    car2.x = 100;
    car2.y = 150;
    addChild(car2);
   
var currentCar:MovieClip = car1;

stage.addEventListener(Event.ENTER_FRAME, onFrameEnter);

function onFrameEnter(evt:Event):void {
    currentCar.x = mouseX;
}

addEventListener(MouseEvent.MOUSE_DOWN, onAddChild);
function onAddChild(evt:MouseEvent):void {
    currentCar = evt.target as MovieClip; //casting
    evt.target.addChild(trailer);
}