Treehouse Of Horror XVI - S17-E4
Mayor Quimby: And now the finalists for Best Costume. First, we have Blacula.
Dr. Hibbert: Oh, because I'm black and I'm Dracula, that makes me Blacula?
The Wettest Stories Ever Told - S17-E18
Flanders: We Puritans have no place for drunkenness, or colorful clothes, or dreaming or poetry. So if you write a sonnet, keep it under your bonnet. Oh no! That was a poem. [Flogs himself].
Answer: I'm not sure if this is the one you're thinking of, but an episode of "Ray Bradbury Theatre," called "A Sound of Thunder," dealt with a similar matter: a group of hunters travel back in time to hunt dinosaurs, only to find things have changed when they get back because someone stepped on a butterfly.
Xofer