Groundskeeper Willie: Yeah, I bought your mutt, and I 'ate him. I 'ate his little face. I 'ate his guts. And I 'ate the way he's always barking, so I gave him to the church.
Bart: Oh, I see. You hate him, so you gave him to the church.
Groundskeeper Willie: Aye, I also 'ate the mess he left on me rug.
Comic Book Store Owner: Now make like my pants and split!
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