Milhouse Doesn't Live Here Anymore - S15-E12
Apu: Attention American bar devils: it's our anniversary. Free drinks for everyone.
Homer: That's great! I'm honored to drink to Apu and, uh, Apulina. You know, Marge and I have an anniversary coming up.
Apu: I have given Manjula many gifts, including a bouquet of flowers, diamond earrings, and we're going to see Paris... Hilton, in Paris... Texas, on our way to Paris... France.
Milhouse Doesn't Live Here Anymore - S15-E12
Groundskeeper Willie: Brothers and sisters are natural enemies. Like Englishmen and Scots. Or Welshmen and Scots. Or Japanese and Scots. Or Scots and other Scots. Damn Scots, they ruined Scotland!
Skinner: You Scots sure are a contentious people.
Groundskeeper Willie: You just made an enemy for life.
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