Visible crew/equipment: After Rachel puts the videotape in the VCR, when she uses the remote to hit play it cuts to a closeup of the TV, and before the tape starts playing we can see the reflection of the camera dolly and a crew member wearing a white shirt, kneeling on the floor.
Continuity mistake: When Ross turns on the camera and sits down in front of it, "flirting" with it and drinking wine, what you can see on the little camera screen is very different from when they play the same clip on the TV, in which looks like he was sitting much closer to the camera then he actually was.
Other mistake: In series 8, 'The One with the Videotape,' when they are watching Ross and Rachel on the TV and when Rachel (on the video) is discussing the invitations and how Monica didn't shut up about sending them, Chandler points at the TV and makes a kind-of confused face. A few minutes later, just before he says 'Did you do it on our invitations?' the same shot of him pointing and pulling a face comes up. (00:17:05)