Easter egg: On S5 disc 3 go to the menu for Deep Space Homer. Highlight the Play with commentary and then press right. An icon will appear on the right - a picture of Bart's ear. Press enter and you can listen to audio outtakes from James Taylor.
Easter egg: On Disk 3 of Season 5, highlight "Bart Gets Famous" and then press up on the remote, this will highlight the Lisa Lionheart doll, which will say a Malibu Stacy phrase heard in the "Lisa vs. Malibu Stacy" episode.
Easter egg: If you go to "Deep Space Homer" special features (disk 3) go to play episode with commentary then press right. An ear will pop up, when you press it you will hear an audio outtake featuring James Taylor.
Easter egg: On the main menu of every disc it is possible to press up and select certain objects on the picture, and activating these causes an animation involving them. Also if you leave the menu idle for a while animations will happen using the characters or events of the episodes featured on the disc.
Easter egg: On Disc 4 on the Complete Fifth Season, select "Sweet Seymour Skinner's Badasssss Song", and up in the top left corner should be the words '100th episode'. Highlight and select them. You'll get a showing of the episode's animatic with a secret commentary by Matt Groening and most of the show's animators about the production of the episode. They also talk about the effect of the California earthquake on the show's production.
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