Continuity mistake: When Phoebe and Monica are at Monica's table and Phoebe is trying to convince Monica to go on a date with her date's translator, watch Phoebe's arm. She points at Monica when she says, "Don't call him that; his name is Spackleback Larry", but when the shot changes to a side view of them, she has her arm resting on the table with no time to put it down between shots.
Other mistake: When Ross goes to see Guru Saj, he has his 'thing' removed. However, it is really obvious that Guru is not going anywhere near the thing, because you can see that Ross' shirt is still tucked into his trousers, and the Guru just rubs his hands along the shirt.
Continuity mistake: When Chandler, Ross and Monica are in Central Perk discussing playing bagpipes, and Ross says, "Decide whatever you want," he is gesturing with his right hand up and with an open book in his left hand. When the camera angle changes, the book is closed and is now in his right hand.
Continuity mistake: When Phoebe and Ross are standing in front of the screen looking at all the babies and talking about why He and Rachel aren't together, some of Phoebe's hair is in front of her shoulder on the right hand side then the shot changes looking over Phoebe's shoulder at Ross. Then when you see Phoebe again her hair is behind her shoulder yet she has not moved or touched her hair.
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. In the same scene, when the animal control lady arrives, Monica and Phoebe have joined them and they are standing round in the kitchen area. The sofa is still visible in the background but the coat has disappeared without anyone having been near it.
Continuity mistake: In the scene where Monica is explaining to Rachel that she has hired her friend Wendy as her waitress, Rachel is holding a water bottle in one hand and the cap in the other. Monica moves towards her and Rachel is pointing her hand in Monica's direction and then in the next shot we see Rachel from another angle and her hand is holding the cap on top of the bottle too fast to have happened in normal time.
Continuity mistake: Rachel and Phoebe are in the Central Perk, talking about leaving the group, and a jacket and a handbag are hanging on the arm of the chair behind Rachel, slightly to her left. Between shots it changes from just the jacket, then just the handbag and so on. This continues throughout the scene when Ross comes in and Phoebe leaves. As she gets up you see both again, however Rachel does not move enough to just show one and hide the other.
Continuity mistake: When Monica, the fake Monica and Rachel are in the girls' apartment talking about the two Monicas auditioning for CATS, Monica (real) has a baguette and a bowl of sandwich filler on the table. In one shot of all three of them, she opens the baguette and starts filling it, then the camera goes in for a close-up of the real Monica and she opens the same baguette and starts filling it again.
Continuity mistake: When Monica and Chandler are in Las Vegas watching the burlesque show, Chandler turns the light on the middle of the table off to "hide" from his Dad. When Monica calls out saying "Waiter. Waitress.", the light is suddenly back on and remains on for the rest of the scene.