If you've never noticed, animated cartoons are all about "ass play".
The hips and buttocks play a central role in defining the overall gesture and movement of many characters. The way Bugs Bunny's butt sticks out borders on "presenting". (See The Sherman Foundation post on Fashion And Display Behavior.)
The older Looney Tunes cartoons are the best and richest examples of the subtle and pervasive featuring of butts and "ass play".
When characters take on a different persona, pants/shorts/skirts often play a central role in defining that characterization. Much of the slapstick humor in cartoons involves abusing a character's tail and characters being hit in the ass with something.
In contemporary cartoons the ass is celebrated and used overly in comedic gags.
Leave it to the Simpson's not to be subtle about the appearance of a butt.
If you want to see Bugs Bunny's penis Click here!