Continuity mistake: At the rehearsal dinner when Chandler loosens his tie and unbuttons his collar, the tie changes its appearance in the following shots from being tighter to looser several times.
Continuity mistake: When the group is sitting around the table in Monica's apartment playing poker, Monica is making something to eat. When she puts it on the table and sits back, we can see a pile of plates on the table on her right side. But in the next shot, the plates are gone.
Continuity mistake: When Monica comes round to Phoebe's, Phoebe reminds her that she's got to clear out stuff. In this wide shot Monica has both hands by her sides, but when it cuts to her finishing saying "oh right", her right hand is now gripping her bag's strap.
Continuity mistake: Ross, Joey and Chandler are in Chandler and Joey's appartment talking about Ross' decision. Chandler has a green bottle in his hand. He puts it down behind the computer by the microwave, but when Ross starts listing Rachel's "cons" the bottle's suddenly at the opposite end of the counter.
Continuity mistake: As Chandler is writing on the board to remind himself about Joey's audition, the door opens as he's writing "Joey", and there are a bunch of squiggly lines under the y. As Chandler is thinking back at that moment and it moves to present tense, he looks over to the board, and the squiggly lines are different.
Continuity mistake: When they're all sitting together and having pizza, talking about parents, Rachel has no napkin. When she says: "Just think, in a couple of years we get to turn into them", a bunched up napkin appears beside her on the couch. After Chandler's remark it has disappeared again, then it appears and reappears again between shots.
Continuity mistake: When Monica asks Chandler and Joey to take Richard to the Knicks, Joey tells Monica, "We will bring him, but only if he takes the Jaguar." Chandler then drops his head in mortification, and the scene then cuts to focus on Monica's expression. In the right corner of this cut, you can see Chandler is looking ahead, and his mouth is moving as if he is continuing a conversation, but there is nothing being said during this scene. The camera then cuts to a different angle where Chandler lifts his head from the earlier drop just before he speaks to Joey.
Continuity mistake: Ross buys the Ultimate Fighting Combo, a large pop and popcorn at the fight, but when he and Monica sit down, they are never seen again. Furthermore, when Monica talks to Pete at the ring, you can see that the Combo was not set on the floor.
Continuity mistake: When Rachel and Monica are discussing whether or not Rachel should meet Ross at the airport she's taking a bottle of red wine out of the refrigerator, but when she places it on the table in the next camera shot the bottle of wine is suddenly a bottle of white wine.
Continuity mistake: Rachel tells her neighbor Danny that she doesn't know anything about sailing, but later in the series, Rachel teaches Joey how to sail after he wins a boat at a silent auction. She says she learned sailing from her father while growing up.