The One With Ross' Step Forward - S8-E11
Other mistake: In the opening scene when Rachel says "I went from store to store sitting on Santa laps" the camera is out of focus.
The One With The Princess Leia Fantasy - S3-E1
Other mistake: When Phoebe makes fun of Ross' Princess Leia fantasy with the rolls, Rachel tries to stop her; the shots used are the same action, just from different angles. Look at Rachel's hands and the towel in her hand when Phoebe puts the rolls by her ears.
The One With The Free Porn - S4-E17
Other mistake: 10:50pm boarding and departure, but it is broad daylight outside. (00:09:25)
The One With Two Parties - S2-E22
Other mistake: When Ross is at Monica's party getting Mr. Green's glasses and cigarettes he bumps into Mrs. Green and ends up having to come up with an alibi for the glasses and cigarettes. He then puts the glasses on, puts a cigarette in his mouth and says 'In fact I'm gonna go out into the hallway and fire up this bad boy'. At this point he walks past Rachel but he stops still as if frozen mid-step just before the shot cuts to him walking out into the hallway.
Other mistake: When Rachel attempts to board the plane the first time, the man at the desk looks at her passport upside down.
The One With Ross's Inappropriate Song - S9-E7
Other mistake: When Chandler finds out that the video marked 'Monica' is just a football game he says, 'This may be the first time I have enjoyed football.' Although in 'TOW The Football' (season 3) he is quite happily watching the Thanksgiving Day game with Ross and Joey.
The One Where Joey Speaks French - S10-E13
Other mistake: When Joey auditions near the end and Phoebe steps in to explain to the producer/audition guy, she speaks French and the subtitles say, 'He is a little bit retarted' instead of 'He is a little bit retarded.' (00:18:35)
Other mistake: In his apartment from later episodes, Ross' kitchen door is on the same wall as the front door, and it is a long and narrow kitchen, but Ross' apartment is between two others. The floor plan doesn't make sense unless the kitchen is only a foot wide, otherwise it would jut off into the hallway.
Other mistake: In almost every season when the friends are in the coffee shop, it shows a front view of Central Perk; and a lot of times, in different episodes, the same (unaging) lady with blonde curly hair is walking past the shop. There are also a couple of different episodes where two babies with red hair are being carried past the coffee shop.
Other mistake: In the first shot of Central Perk in "The One with the Monkey" and "The One with the Dozen Lasagnas", the same footage has been used twice because the same three people are having the same conversation in both episodes.
The One with the Blackout - S1-E7
Other mistake: Ross says that he was at Disneyland with Carol and got caught hooking up on Small World and asked to "never to return to the Magic Kingdom." Disneyland is in California and the Magic Kingdom is part of Disney World in Florida. (00:06:10)
The One Where Rachel's Sister Babysits - S10-E5
Other mistake: Jennifer Aniston's tan mark from her wedding ring is especially visible in this episode. Most notably when she says "But Erin Brockovich had her own house."
The One With The Embryos - S4-E12
Other mistake: Phoebe takes a positive pregnancy test right after she gets implanted with the embryos. There's no test in the world that can tell that fast if someone is pregnant - even the best tests take at least a week after conception.
Suggested correction: Phoebe explains before she takes the first pregnancy test that her body's "always been a little faster than Western medicine". It's a deliberate joke.
A deliberate joke it may be, but we all know Phoebe believes a lot of silly things, and this is one of them. It really didn't make sense for her to get a positive result that fast.
The One With The Ball - S5-E21
Other mistake: The guys start the ball-throwing game at around 2 in the afternoon. Later, they mention that it's been going for 10 hours, making it around midnight. Why would Rachel, who never cooks, be defrosting a chicken? And why would she be doing so at midnight?
The One With The Dollhouse - S3-E20
Other mistake: The dollhouse is only partially burned when Ross takes it into the bathroom to extinguish it. When he shows it to Phoebe it's completely blackened and destroyed. He and Monica wouldn't have just let it burn; they would have extinguished it ASAP, and there's no reason why that wouldn't have been fast if they doused it in the shower.
The One Where Ross Dates a Student - S6-E18
Other mistake: Ross' semester supposedly just ended, and he's handing in his grades. But the episode just before this one was about Valentine's Day, and the one immediately after this one is about spring break, so this episode is happening sometime between mid - February and March/April. It doesn't matter when the show was aired or produced; Valentine's day is still in February. There's no semester that ends at that time of the year, and NYU wasn't on the quarter system then.
Suggested correction: This episode (production code 225567) was produced before episode 17, "The One With Unagi", (production code 225568) and just aired out of order. So this episode happens before Valentine's Day.
The One with the Blackout - S1-E7
Other mistake: When Ross and Rachel are out on the balcony alone for the first time, there are no lights on in NYC apart from candle lights. Look in the BBQ behind them though to see a very bright and very white light reflected in the paintwork. (00:13:50)
Other mistake: In "TOW the cheap wedding dress" the whole episode is about how Chandler wants "The Swing Kings" to play at the wedding, because, at their concert, that is where he realised that Monica was the woman he wanted to dance all his dances with, and Monica goes to great lengths to secure the band. In this episode, the band at the wedding is actually called "Jungle Swing".
Suggested correction: So the band changed their name in the interim. It happens.
The One With Mac & C.H.E.E.S.E. - S6-E20
Other mistake: When we see the chess board at Central Perk that Ross and Chandler are using, the black pawn in front of the black knight nearest the camera is missing, and from the arrangement of the white pieces, it cannot have been captured yet.
The One Where Rachel Finds Out - S1-E24
Other mistake: When Rachel leaves the apartment to pursue Ross to the airport, she is turning to the left when she exits the apartment. The stairs are to the right.
