Visible crew/equipment: When Rachel opens the door to the apartment while she's holding flowers and sees Phoebe trying to get up from the couch (before the wedgie comment), the open edge of the set wall can be seen at the top left corner of the screen.Super Grover
Continuity mistake: On the actual prom video tape, it only takes Ross a mere 12-13 seconds to run up the stairs, completely change outfits into his Dad's tux, and reappear ready-to-go on the stairway. This is impossibly fast. Also, it is not possible that the prom video tape was stopped and re-started during this time, which could account for the short duration. The reason is because Ross's mom was the one filming at this point. It turns out that she has no idea how to stop the video recorder. Thus, the video tape was one continuous recording, and we are expected to believe that Ross could change outfits within 12 seconds. (00:21:25)
Continuity mistake: It's obviously December, with the set decorations and Rachel's reference to sitting on multiple Santas' laps because she is randy from her pregnancy hormones. The characters establish that it's Rachel's fourth month of pregnancy...but she became pregnant about six weeks before Monica and Chandler's May 15 wedding. Her fourth month would have been in July, not December.MovieFan612
Continuity mistake: When Rachel is talking to Joshua near the drinks table at the party, he is holding a blue cup in his left hand and nothing in his right (this is most obvious when she's offering him a cherry). When she begins to choke, he raises his empty right hand to pat her on the back, then when she walks away there is suddenly a bottle in his raised hand. The shot changes, and his hand is again empty and he reaches down to the table and picks up the same bottle. (00:08:30)
Continuity mistake: When Monica says, "I just recently got out of a serious relationship," she is holding her glass in her left hand. The camera cuts to Pete and the glass is now in her right hand. It then switches back to her left hand in the next wide shot.wHw
Factual error: Phoebe discovers that one of the babies has wandered away, and finds the baby inside the open drawer. Yeah, no. These babies aren't even walking yet, much less are they able to lift themselves up past the height of their own bodies and launch themselves into a drawer.
Factual error: The restaurant refuses to take anyone's orders until they're all seated, which means that the group is sitting, occupying a table, without earning any revenue for the restaurant. There isn't a restaurant in NYC that would have such a policy, since it basically guarantees that a table becomes a revenue vacuum. (It also makes for very unhappy customers, but that doesn't qualify it as a factual error, since some restaurants might be actually stupid enough to not care about their return customers).
Revealing mistake: In the scene where Chandler confronts Janice about Joey seeing her kissing her ex-husband, Janice begins to hyperventilate. However, right before Chandler gives her the paper bag, Janice spins around and places the receipt in her mouth. Conveniently, after she begins breathing into the bag, she "chokes" on a receipt.