Continuity mistake: When Phoebe is talking to Ursula's fiance Eric, he is wiping sweat off his face with a napkin. He puts the napkin to his eye and then in the next shot it changes to the other eye without him having enough time to change it. This happens again when at one point he's wiping his eye and then suddenly his forehead.
Continuity mistake: When Monica takes off her belt and throws it onto the couch, it lands on Rachel's arm. Throughout the scene, between shots of Rachel and Monica talking, the belt constantly disappears, reappears and changes position without Rachel ever touching it.
Continuity mistake: Rachel is talking to Joey in his apartment after waking up the next morning, looking messy and rumpled. As she talks, her bra strap slips down her arm. In one shot (as she says "I'm a horrible person"), the strap is all the way down her arm and then in the next shot it is tucked under her shirt.
Continuity mistake: When Phoebe tells Ross that she wants to hear his "sound", she has her guitar in her lap. The shot changes, she says "Play that funky music white boy," and her guitar is missing. In the next shot, Ross runs out and her guitar is back on her lap again.
Continuity mistake: When Ross is asking Joey and Chandler which suit he should wear for the TV thing the brown suit is in his right hand and the blue one is in his left hand. After Ross says "really?" the shot changes to a wide view, the two suits have changed places, and the cover on the brown suit has switched to the blue one.
Continuity mistake: When Phoebe is in the coffee house talking to her father and pretending to be the executor of her grandmother's will, after she says "lipstick and a daughter, big day for you" she folds her papers in half, but in the next shot they are unfolded and she then folds them again.
Continuity mistake: Monica and Chandler are piling their dinner plates with food while arranging to meet for a second quickie. Chandler's plate is stacked with various items when he agrees to meet Monica in the cellar, but when he tosses his plate back onto the table to rush off without eating anything, the plate is nearly empty.
Continuity mistake: In TOW the lottery tickets series 9 just after Chandler has got the job and he sits down you can see Joey's hand in the right side of the screen however when the shot changes Joey moves his hands up to the position we have just seen. The shot changes back and his hand is in the same position.
Continuity mistake: When Charlie and Benjamin are at the restaurant, Benjamin says "I can't believe you chose this restaurant. You remember that night?" To which Charlie replies "I can't believe they let us back in here." However in "The One with the Fertility Test" Charlie has never been to New York before.