Tree House of Horror X - S11-E4
Continuity mistake: The broken railing in front of Lucy Lawless returns to normal when the shot changes after the Collector lands on the computer.
Tree House of Horror X - S11-E4
Continuity mistake: In "Desperately Xeeking Xena", as Lucy Lawless grabs the lips of the Collector, you can see a big "C" on the back of his cape. After she has thrown him across the room and he gets up, the "C" is gone. It reappears later in the fight.
Tree House of Horror X - S11-E4
Continuity mistake: When The Simpsons go home they find the words 'I know what You Did' on their door, written in blood. Then another shot after, you can see the door with nothing on it.
Tree House of Horror X - S11-E4
Audio problem: In "Desperately Xeeking Xena", Xena is put in a plastic pouch. Wouldn't her voice sound muffled?
Tree House of Horror X - S11-E4
Other mistake: In "Desperately Xeeking Xena", at one point she approaches the Collector, who is about to get a light saber. We can see the back of the pouch that Xena is in, but the tape on the other side isn't visible, even though it is a transparent pouch.
Tree House of Horror X - S11-E4
Continuity mistake: In the 'I know what you did-diddly-did' story, the Simpsons car keeps changing from dark purple to the normal pink colour.
Tree House of Horror X - S11-E4
Continuity mistake: In the flashback, the car moves a lot further than it did originally after hitting Ned.
Tree House of Horror X - S11-E4
Continuity mistake: When The collector falls over the banister and into the Lucite, Xena is taped into a plastic pouch; but when she gets out, she pulls the bag down easily, without ripping open the bag or the tape.
Tree House of Horror X - S11-E4
Continuity mistake: When Marge hits Ned Flanders, she pulls over, in the middle of the road. But When they go to see who they've hit, and when Homer picks Ned up and 'talks' to him, the car has disappeared from the road.
Tree House of Horror X - S11-E4
Continuity mistake: While the Simpsons are standing in the line, waiting to enter the rocket to Mars, you can see Professor Frink wearing a white shirt. However when he enters the lift to the rocket, he has a green shirt on.
Tree House of Horror X - S11-E4
Continuity mistake: When the flashback of running over Ned happens his jumper is ripped and sleeveless because he has just been a wolf. Earlier though when the Simpsons find him, his jumper is not ripped.
Tree House of Horror X - S11-E4
Continuity mistake: In "I Know What You Diddly-Iddly Did", there are a few errors: Homer says, "Guess I forgot to put the fog lights in" at a slightly higher pitch to when we heard him say it earlier (When the event actually happened). When Marge actually ran over Ned she did not carry on driving. The flashback shows that Ned was run over without glasses. However in the actual event he had glasses on.
Tree House of Horror X - S11-E4
Continuity mistake: In "I Know What You Diddly-Iddly Did", just after Ned has been run over, he turns from a werewolf into his normal self. If you look carefully, his left ear turns brown for a second before turning yellow again.
Tree House of Horror X - S11-E4
Plot hole: In "Life's a Glitch", Lisa finds out that she has a seat on the spacecraft going to Mars as the proofreader. How, though, was she not informed of this before going to the rocket? The family only finds out about the rocket after finding Krusty's letter/invitation and the fact that she was on the list there would be no reason why she wouldn't have been informed of this. It was still New Year's Day so if it had been by mail then it would have to arrive before the New Year so as to make the plan work, being as it was a public holiday and no mail would be delivered. Therefore it would have to be delivered personally or someone would need to contact her. There were also many well known celebrities and figures ready to board the rocket. I can't imagine they were all home in time to gather their mail and were all somehow contacted, yet Lisa was simply walking around town and at church and they couldn't find her? There was also no evidence to suggest anything would have stopped her from either receiving the invitation in time or being informed of the mission.
Tree House of Horror X - S11-E4
Character mistake: When the Collector is putting Lucy Lawless into her plastic bag in his lair with the other celebrities, he refers to Tom Baker as "Doctor Who." As a sci-fi nerd, he would know the character's name is simply "The Doctor."
Tree House of Horror X - S11-E4
Continuity mistake: In "I Know What You Diddly-Iddly Did", Marge's necklace keeps changing from red to white when the Simpsons are at church, and when they go back home.
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