Corrected entry: At the end of the episode, Ross and Monica complain because they didn't get to perform their routine on the platform (because it cut to midnight too quickly). But the director must have known exactly when the filming would end, so why would he have put Ross and Monica on the platform 10 seconds before the end of filming? It's not just that he wants them in the background for a few seconds or something, because he wanted them for the blooper show (not the final show) and they didn't get a chance to dance up there at all.
Corrected entry: Towards the end of the episode, when Chandler comes into the apartment to talk to Joey about his kiss with Kathy, Joey turns the TV off and places the remote on the counter. However, the TV is suddenly back on after Joey asks, "Is that why you bought all this stuff?" (referring to the furniture), and then Joey turns it off again manually. (00:17:10)
Corrected entry: When Ross and Joey are auditioning for Monica's maid of honour, Rachel says she met Monica when they were 6 and she met Chandler when he was 25, but in other episodes it shows that they had been to thanksgiving dinners together when Chandler was in college with Ross. In another episode it also shows Chandler and Rachel making out at a party, so she had met him plenty of times before he was 25.
Corrected entry: When Monica and Ross are discussing why they are not allowed to play football, Monica states in the story that they were both 6. This would imply they are either twins or at least the same age. However, we see that Ross is in fact older than Monica. Also, later in the scene Monica and Ross say the football incident occurred 12 years ago. This would mean that they are both currently 18 years old which is false. In one episode earlier in the season Monica states that she is 28 years old. (00:02:20 - 00:04:10)
Corrected entry: Monica tells the guys that she and Phoebe will search the third and fourth floors for the monkey and the guys would search the first and second floors. But Monica and Phoebe knock on Mr. Heckles' door, #9, which would be on one of the lower floors.MovieFan612
Corrected entry: Across the whole show, the infamous wall in Rachel's room / guest room (Monica's apartment) changes. When the room is not being filmed, the wall is as normal, but on quite a few episodes, when the room is actually used for scenes, the wall is much shorter. In both the episode where Ross buys Phoebe a bike, and where Phoebe and Rachel have to live with Monica after their apartment caught on fire, people are able to walk straight into the room without the wall being in the way.