$pringfield (or How I Learned to Stop Worrying and Love Legalized Gambling) - S5-E10
Trivia: Towards the end, Mr. Burns starts becoming insane, growing long hair and long, claw-like fingernails and toenails, and becoming obsessed with germs. This just what happened to Howard Hughes, the eccentric billionaire who died in 1976. Burns also has a plane called the "Spruce Moose." Hughes' plane was the "Spruce Goose," currently displayed in Long Beach, California.
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.
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