Continuity mistake: In the scene when Joey and Chandler come into the cafe to say that Marcel got into San Diego zoo, the man who wants him for animal fighting turns and says that Ross is making a big mistake. At this point the monkey starts to go down Ross's arm and almost drops off but in the next shot he is far up on his shoulder again. (00:14:40)
Continuity mistake: When Ross say 'just a smidge' after Rachel says Paulo named her breasts, Phoebe is holding tinsel and Rachel is looking at Ross. In the next shot, Rachel is looking in the opposite direction and the tinsel has vanished from Phoebe's hands. (00:06:00)Dwarf
Continuity mistake: During the Monopoly game (deleted scene), right after Monica says, "we can bring my wheelbarrow, to carry your teeth," we see Ross reading the game manual at the end of the shot. At the beginning of the very next shot, he is suddenly rolling the dice with no manual in his hands.
Continuity mistake: When Ross comes back to Monica and Rachel's apartment and Rachel tells him she has lost Marcel, he takes off his overcoat and lays it over the back of the sofa and then sits by it. As the scene continues, the sofa is still visible in some shots and the black coat is crumpled up on the sofa cushion. (00:11:25)
Continuity mistake: When Joey is talking to Ross and Chandler about missing Phoebe's birthday, Chandler has the newspaper in his hands. In the next shot, you can see that Chandler does not move at all, then in the next shot, the paper is on the table. (00:04:35)Dwarf
Continuity mistake: In the scene where Rachel and Ross are playing poker head to head, Rachel borrows $7 from Monica's purse and then puts the purse down on the table. She puts it down on her left hand side but it then switches to her right hand side without her touching it and then back again. (00:22:25)