The One With Mac & C.H.E.E.S.E. - S6-E20
Visible crew/equipment: A stage light can be seen at the top left hand side of the screen just after Joey slams the door shut after practising a scene with Phoebe. It is visible in front of the blue picture on the wall.
The One With The Ultimate Fighting Champion - S3-E24
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.
The One With The Princess Leia Fantasy - S3-E1
Continuity mistake: In the seen where Monica is shouting "why hasn't he called" she is holding a juice bottle, but when the shot cuts to Phoebe she is holding a glass.
The One with the Dozen Lasagnas - S1-E12
Visible crew/equipment: When Joey and Chandler walk into their apartment and the table falls over when Joey puts the key on it, the edge of the set and studio lighting are visible at the top of shot. The end of the set wall is also visible at the right side of shot. (00:04:50)
The One With The Cooking Class - S8-E21
Revealing mistake: Just as the scene cuts from the streets to the baby store, the camera wobbles slightly.
The One With Ross's Grant - S10-E6
Continuity mistake: When Phoebe tells Rachel and Monica that Mike lets her keep her box of hair, Rachel's chopsticks are down, by the plate. In the next shot, she's holding them close to her mouth.
The One With Ross's Library Book - S7-E7
Visible crew/equipment: When Chandler puts a plate down next to the Chinese food, and Monica walks in a boom mic can be seen over her head. (best on DVD). (00:06:20)
The One With The Soap Opera Party - S9-E20
Visible crew/equipment: When the roof party begins, above the door a boom mic is visible.
The One With The Birthing Video - S8-E15
Continuity mistake: When Chandler tells Rachel and Monica to look at the screen when the baby has come out, his arm goes from pointing at the TV to on his lap.
The One With Rachel's Crush - S4-E13
Visible crew/equipment: When Monica is wafting the smell of cookies to the other in the big apartment, there is a shot of Monica, and all the stage lights are reflected in the TV screen. (00:09:55)
The One In Barbados, part 2 - S9-E24
Continuity mistake: At the end of the ping pong scene when Chandler wins, a paddle appears on the floor for one shot then disappears in the next. No-one had time to touch it. (00:44:20)
The One with the Monkey - S1-E10
Continuity mistake: Just before the opening credits, when Ross says, "That's 'pathet', which is Sanskrit for 'really cool way to live', " Marcel is sitting on Ross's left shoulder in the closeup, but in the next shot the monkey is suddenly sitting on his right shoulder, right before Ross walks off screen. (00:01:00)
The One With Rachel's Crush - S4-E13
Other mistake: Monica supposedly single-handedly changed over the guys' apartment from carpet to polished hardwood in two days. There's no way that someone of her size could have moved all that furniture solo (Rachel didn't help since she's totally surprised), stripped off all the carpet, sanded the wood, stained the wood, let it dry, and then replaced all the furniture, in two days.
The One With The Dirty Girl - S4-E6
Other mistake: When Rachel tells Joey he can't get Kathy another "coupon for an hour of Joey love", you can see Chandler (Matthew Perry) mouthing the words "Joey love". (00:17:21)
The One With The Fake Party - S4-E16
Factual error: Phoebe says in the show that she's three months pregnant. Not only is she way too big for that, but the fetus also kicks for the first time. Women don't feel fetal movement until 16 weeks at the earliest, and for a first pregnancy it may not be until 25 weeks or so.
Suggested correction: Phoebe's size could partially be explained in that she was carrying triplets, though Lisa Kudrow was pregnant in real life, and was further along than her character. Her pregnancy had to be written into the show and the gestation timelines did not match up. Phoebe feeling "movement" could just be her imagination, as her character is supposedly somewhat psychic and often perceives things that are not necessarily discernible to others or isn't even real.
Even if the actor was further along than her character, that doesn't make it a mistake.
Continuity mistake: When Chandler's partner says she's going to be late for Andrew she has her hands in front of her. Camera changes and now one hand is up by her hair. (00:18:15)
The One With The Giant Poking Device - S3-E8
Factual error: The "very long poking device" that the friends fashion out of chopsticks would never actually work. It has vulnerable points every half-foot or so (the length of the chopsticks) and after a certain point would just break or sag under its own weight at one of the vulnerable points.
The One With Ross's Teeth - S6-E8
Character mistake: While on his date with Hillary, Ross says that he has a five year old son. Ben was born in 1995 and this episode is set in 1999, so Ben should be four, not five.
The One With Joey's New Girlfriend - S4-E5
Continuity mistake: When Ross goes to Amanda's house for a date you see her two children sitting on the couch. The little boy with blonde hair is sitting down, when it cuts to Ross and Amanda talking the boy is standing up on the couch, the next shot he's sat down as Amanda walks out the door.
The One With The Screamer - S3-E22
Factual error: Rachel's date yells at the theater patrons who are in the gang's seats; one of them has D13, and he screams "you're surrounded by even numbers, does that give you some clue?" However, the establishing shot shows they're at the Lucille Lortel Theater, which has odd-numbered seats on the left - the side they're sitting on. It is also a relatively small house and doesn't have a D13; the outermost seat in that row is D9. (00:04:50 - 00:05:30)
