The One with the Thumb - S1-E3
Factual error: The show is set in New York. Joey was a cast member on Days of Our Lives, which is filmed in Los Angeles, but is still always around.
The One with the East German Laundry Detergent - S1-E5
Character mistake: In the laundromat, there is a sign where the word clothes is misspelt cloths. (00:16:00)
The One With The Truth About London - S7-E16
Audio problem: During Rachel's scene sitting on the couch with Ben talking about her and Ross and her sisters, Rachel's mouth moves in any scene showing Ben, but without her being heard.
The One With The Video Tape - S8-E4
Audio problem: When Joey says "this is not fair to her, let's just forget the tape", his mouth stops moving after he says "forget", making it look like the audio is coming from nowhere. (00:12:07)
The One After Ross Says Rachel - S5-E1
Audio problem: Monica tells Ross that he should keep looking for Emily, and Chandler says "Yeah, for about 30 minutes." But the audio doesn't match up with his lip movements, indicating this line was dubbed. (00:10:26)
The One The Morning After - S3-E16
Visible crew/equipment: When Phoebe says they've been quite for a long time, a boom mic is visible above her (only visible in fullscreen version). (00:21:40)
The One With The Proposal, part 2 - S6-E25
Audio problem: In the pizza place, after Chandler tells Monica to "put down [her] copy of The Rules..." you hear Monica say, "You know what. I gotta go" when her lips aren't moving. (00:04:26)
Other mistake: When Joey sat in the paint the first time, there was a mark, but the second time, it didn't leave a mark.
The One Where No One's Ready - S3-E2
Visible crew/equipment: When Ross tells Chandler and Joey, "I'd feel a whole lot better if you got dressed now," the reflections on the TV screen show there's a crew member at the side of the sofa wearing a white T-shirt, as well as the camera and camera operator behind the sofa. (00:00:30)
The One Where No One's Ready - S3-E2
Visible crew/equipment: After Rachel agrees that it will indeed take her 6 or 7 minutes to get dressed, with the caveat, "Once I figure out what I'm wearing," it cuts to Joey offering Ross the "glass of fat" as he stands behind the couch. In the next shot of Ross, the reflections on the TV screen show Joey is still sitting on the couch, and the camera and camera operator (wearing a dark shirt and raises an arm) behind the sofa. (00:01:15)
The One Where Joey Dates Rachel - S8-E12
Factual error: The premise of Chandler filling the high score list with dirty words is not possible for this game. Ms. Pac-Man only keeps track of a single high score, which is always displayed at the top of the screen. Unlike many other games of the era, there is no screen showing a list of additional top scores alongside initials during the attract mode, and there is not even a mechanism for entering initials within the game's code.
The One With The Bullies - S2-E21
Visible crew/equipment: When Chandler falls behind the couch, the mat he lands on is visible.
The One With The Tiny T-Shirt - S3-E19
Audio problem: When Joey chants "Oh Mommy, Oh Daddy, I am a big ol' baddie" his voice doesn't match his lip movements.
The One with George Stephanopoulos - S1-E4
Continuity mistake: When Rachel is explaining that she's not going back home, the friend with her arm on the back of the sofa behind her has her sleeve part the way up towards her elbow leaving a very prominent gap between the sleeve and bracelet. When the camera comes back to her the gap has now gone. (00:08:20)
The One with George Stephanopoulos - S1-E4
Continuity mistake: When Rachel's friend who is pregnant appears in Central Perk, she says she's like a Duplex. When she does, her left-hand goes from outstretched to on her belly. (00:06:10)
The One Where Monica Gets a Roommate - S1-E1
Audio problem: When Phoebe says "I just don't want her to go through what I went through with Carl" the camera cuts to Chandler's reaction. When you look at the bottom Phoebe's mouth is moving even though she's not speaking. (00:01:39)
The One Where Ross Got High - S6-E9
Audio problem: When Ross and Joey go into the bedroom, you can hear the duck in the background, even though the chick and the duck should be in the other apartment and aren't even in this episode. (00:12:53)
The One Where Monica and Richard Are Just Friends - S3-E13
Revealing mistake: When they are in the coffee house and go over to the counter to discuss Phoebe's boyfriend's exposure out of his shorts, in the long shots you can see behind that there is no way they would be able to see anything.
The One With Frank Jr. - S3-E5
Other mistake: Monica doesn't realise what the floor looks like under the hamper, but due to her obsessive cleaning she would know this for sure.
Factual error: The makeup on Rachel's face "can't be covered up with makeup," and "won't come off," we learn in The One In Vegas, Part 2. So it's not a surprise that she still wakes up with it on (and so does Ross.) but an hour or so later, when she's at breakfast, it's not there. An hour or two won't make the magical difference that 8+ hours didn't.
