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)
The Silver Surfer & the Coming of Galactus: Part 1 - S1-E5
Continuity mistake: When the Four are looking out the window and observing the burning sky, Reed is incorrectly depicted with blonde hair. When the shot changes, his hair is back to being brown, but now the white streaks in his hair are also brown. (00:05:18)
Sins of the Fathers Chapter 3: Attack of the Octobot - S3-E3
Continuity mistake: When Doc Ock is about to unmask Spider-Man in his lab, there is a brief shot of Doc Ock standing under a night sky. This is from their rooftop battle in the previous scene/episode.
Silence My Companion, My Death Destination - S1-E4
Continuity mistake: When the general is putting his sunglasses on, they resemble safety goggles. When the shot changes, they look more like aviators. (00:01:50)