The Springfield Files - S8-E10
Kent Brockman: Tonight on eyewitness news: a man who's been in a coma for 23 years wakes up.
Coma patient: Do Sonny and Cher still have that stupid show?
Kent Brockman: No, she won an Oscar and he's a congressman.
Coma patient: Good night! [Flatlines].
The Springfield Files - S8-E10
Leonard Nimoy: The following tale of alien encounters is true. And by true, I mean false. It's all lies. But they're entertaining lies. And in the end, isn't that the real truth? The answer is no.
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