Continuity mistake: At the beginning when Rachel and Monica talk about the free coffee sample, Rachel puts it down on the counter to her right. In the next shot it's lying to her left with no time to have gotten there. After that it switches from the right to the left and back again. (00:01:25)Babatomyfriends
Continuity mistake: Just after Rachel has tried to whistle and just blew out crumbs, she picks up the fork with her left hand and places it to the left of the cake on the kitchen counter. In the next shot just before Chandler picks up the cake the fork is back on the right side of the cake near her right hand. (00:16:05)Babatomyfriends
Continuity mistake: In the scene where Phoebe tells the gang about her "Relaxitaxi" idea the position of Chandler's left arm changes between shots. In the frontal shots it's lying the back of the chair and in the shots from behind it's wrapped around Monica's shoulder.Tanngrisnir
Continuity mistake: In the beginning of the episode when Joey tells Chandler that he hasn't forgiven him for kissing one of his sisters, Monica and Chandler's TV, entertainment set and ferns are missing from the set and there are cables protruding from the wall. The area is completely bare except for the French poster. Everything's back to normal slightly later in the episode.
Other mistake: When Ross is at Monica's party getting Mr. Green's glasses and cigarettes he bumps into Mrs. Green and ends up having to come up with an alibi for the glasses and cigarettes. He then puts the glasses on, puts a cigarette in his mouth and says 'In fact I'm gonna go out into the hallway and fire up this bad boy'. At this point he walks past Rachel but he stops still as if frozen mid-step just before the shot cuts to him walking out into the hallway.Professor Lazarus
Continuity mistake: Just after the opening titles cut to Central Perk, four people can be seen having a conversation through the window. In the next shot, there is one person sitting next to the window and a waitress has appeared out of nowhere. (00:03:05)Casual Person
Continuity mistake: In the opening scene in Central Perk when Paul (Elizabeth's dad) takes Ross to one side to talk to him you can see the girl in the blue top enters the door twice: first the shot after Paul says "I'm funny like that" and then again after Ross says "I realise it upsets you".