The One With the Sharks - S9-E4
Revealing mistake: While Monica and Rachel are talking about Chandler's "jollies to Jaws" Rachel's wearing a colorful flowery top, and after Joey walks in just as Monica takes her seat at the table in the closeup, it's Jennifer Aniston's stand-in, wearing a blue top, who is seated beside Monica. Rachel's hair is wavy in the flowered top, but straight in the blue top (viewed in widescreen). (00:12:22)
Visible crew/equipment: When the son of the accident victims is being led through the trauma rooms to see his parents' bodies, you can see Laura Innes crouching under a table in the background directing the scene. Innes was the director of this episode and it was established that this episode took place on her character's day off. Therefore, she should not have appeared in front of the camera at all. (00:32:30)
Partners in Danger Chapter 5: Partners - S4-E5
Continuity mistake: When Smythe is discussing his plan with the Silvermanes, his yellow eyes are blue in one shot.
Enemy Within, Enemy Without - S1-E6
Revealing mistake: When Iron Man tells MODOK that his wife is waiting to see him, MODOK's nose and a section of his headband are briefly missing from his face. (00:19:49)
The Origin of the Fantastic Four: Part 1 - S1-E1
Factual error: After the group has crash-landed back on Earth and Sue is saying "We're all alive," the moon behind everyone is far too large. (00:06:34)