As you stare at your suddenly much-younger self, you realize that the costme is starting to look more realiztic. The baggy fake fur is starting to draw in around you, and the hair doesn't look quite so fake. And your face looks weird, as if it is pushing out. Your nose and mouth are getting darker, and your hands and feet feel heavier.
When you feel your long donkey ears twitch, you realize that the costume isn't of a little boy in donkey suit - it's that of a baby jackass - and if you don't get it off right away, that's exactly what you will be!