Smoother animation is the key to good animation. When you use the smoother animation key, transport it to the costume's door, not the backdrop. Open the door of the costumes, and then create your costumes by looking at Google images for help. If you already know what what you want to draw looks like, just draw it. Make your animation smooth and not choppy. (PS the key and doors are metaphorical plz don't think there's a door in scratch XDXD messin' w/ u)
You can use the new animation or the original but smoother.