Brother Can You Spare Two Dimes? - S3-E24
Mr. Burns: Before you begin, let me make one thing clear to you. I want your legal advice, I even pay for it. But to me you're all vipers. You live on personal injury, you live on divorces, you live on pain and misery. But I'm rambling. Anybody want any coffee?
Lawyer: I'll have some coffee.
Mr. Burns: Want it black, don't you? Black like your heart. It's so hard for me to listen to you, I HATE YOU ALL SO MUCH.
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