Lucy is a sweet girl, full of energy and very smart.
She love to talk and explain all sort of stuffs, sometimes making her very annoying, but her hearth is always in the right place.
Her body is extremely soft, that makes her very easy to squash or flatten.
Being hit by an opening door or something heavy falling on her is enough to turn her into a pancake, so it happen a lot...
She's also easy to inflate like a balloon, just blow into her mouth and here she goes, floating away.

(It's a basic sketch, maybe I'll make a better pic later)