Visible crew/equipment: Just after Chandler says "I'm the smallest person in the world", and Joey comes out of his room, check the top left of the screen - you can see a boom mic track Matt LeBlanc across the set, and the bottom of some stage lights in the middle.
Continuity mistake: When Phoebe and Chandler are about to kiss there is a bottle of wine and two glasses on the counter. It then cuts to a view of Phoebe with no bottle or glasses on the counter, just a phone, and then later in the same scene it cuts back to Phoebe again and there are two glasses and a bottle of wine again.
Continuity mistake: When Monica returns from work to find that Chandler has been playing on Ms Pac Man all day, he lifts his hand and it is in a claw shape, which Monica comments about. However, when he and Monica are talking you can see the same hand and it's fine. He points to the screen of the game with it, and is also seen putting it into his pocket. When Phoebe enters later and asks why Chandler has suddenly gotten so good at the game, he shows her the same hand...the claw is back
Continuity mistake: The night before they go to the baby furniture store, Ross and Rachel are in the kitchen talking. Just before they leave the kitchen watch Rachel's robe: in one shot the 'lapels' are neatly one over the other, and in the next shot one lapel has moved lower and looks halfway folded over as if she hastily pulled the robe together.
Continuity mistake: When Monica and Phoebe are eating with the diplomat and his translator, watch the translator's chocolate cake. It either rotates, has some taken out of it, or is a different piece. Whichever way, the cake changes size, shape or position without him ever touching it.
Continuity mistake: When Monica is at the party and she is drunk, there is one point when she is sitting down on a chair with Chandler on her right. Chandler is holding her left hand (which has a snack in it), but when it cuts to a front view of Monica, suddenly both her hands are on her lap.
Continuity mistake: In the one with Rachel's new dress, she's in her underwear on the sofa when Joshua comes in. In wide shots focusing on Joshua she's quite laid back, but in close shots of her she's sitting more upright. Worse than that, her legs are crossed, but uncross in the shot of his parents coming in, only to re-cross in the next shot when she gasps.
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: There is a long shot of Rachel and another person sitting on the sofa and Rachel's wine glass is almost empty. She then goes over to the the counter to fill it up. However, before she starts to fill it, a significant quantity of wine can be seen in the glass.