It's been a long while since I've seen much of the Simpsons. The series continues to lack the soul and wit of the earlier seasons, but it's good to see their heart is in the right place:
In what I imagine was a lame attempt at a Marge joke, she wonders, "what evolution will make next? Maybe a bird with a people's face?" I couldn't help but think of Japan's Heikegani or samurai crab.
This species likely evolved its peculiar body shape following many generations of unintentional artificial selection.
EDIT: Oh fiddlesticks. It seems the truth about the samurai crab may be much more coincidental. Interestingly, I picked up this example from the very same Carl Sagan program!