The scene I'm talking about features Mrs. Incredible (aka Elastigirl), who is sneaking into an enemy base when she unexpectedly catches sight of her ass in a reflective surface, thus:

She doesn't seem to care for what she sees, either. She sighs. Heavily.
Well, why the sigh, Mrs. I?
You have, by definition, an Incredible ass -- among the very finest cartoon asses I've ever seen. I'm in your yard the minute I see that milkshake. What's more, when you walk in with that itty-bitty waist and a round thing in my face, what do you suppose I get?
That's right, baby. Sprung.
Also, if you don't like your ass, why not just reshape it into something you do like? You're Elastigirl. You could easily reshape your ass into
a. Daisy Duke's ass
b. Jennifer Aniston's ass (the original boo-tay, not the abridged Mrs. Pitt edition)
c. J. Lo's ass
d. J. Lo's head
e. Shaquille O'Neal
You're a woman who can slide under a locked door and make balloon animals out of your fingers, right? For you, a little improvised butt-mod should be nothing.