
The One With The Metaphorical Tunnel - S3-E4
Revealing mistake: While Chandler and Janice are in D'Agostino's, some grocery products have their names partially covered, such as Uncle Ben's and Grape Nuts.
Trivia: The artwork on the wall behind the couch in the coffee house changes every 6 episodes
Suggested correction: That's not really trivia nor a continuity mistake. Small businesses, particularly cafes and coffee houses, often show different local artists' work on a rotating basis in an effort to support the local arts.
How often it's rotated could be considered trivia however.
The One With The Girl From Poughkeepsie - S4-E10
Factual error: Ross falls asleep on the train and ends up in Montreal, where the woman he meets tells him "it's only a 2-hour ferry ride to Nova Scotia." Yeah, more like a journey of between 13 hours (12-hour car ride plus 1-hour ferry) and 23 hours (multiple bus legs plus 1-hour ferry.) The character could have been lying to Ross, but it's not presented that way at all.
Suggested correction: It's presented as sarcasm. Not a mistake.
Not clear on where you got that it's presented as sarcasm; nothing in her delivery says so.
The One with the Dozen Lasagnas - S1-E12
Plot hole: At the end, Phoebe and Monica are sitting at the table eating the meat lasagna. Phoebe would not eat this as she is a vegetarian. (00:21:35)
Suggested correction: Early on in the episode, Monica suggested vegetarians can scrape. It is possible that Phoebe is doing exactly that. Also, two episodes later ("The One with the Candy Hearts"), it is revealed that Phoebe, in fact, does enjoy meat, as long as no-one tells her it is meat she is eating. She is poor and has never been able to afford meat.
The One With The Embryos - S4-E12
Character mistake: After the guys have beaten the girls in the quiz, Rachel refuses to move apartments and Monica says: "If we had lost, we would have made them get rid of the birds." But they did lose. That's why the guys have got their apartment. She should have said if we had won.
The One Where Monica and Richard Are Just Friends - S3-E13
Factual error: Joey refers to several of his favorite parts of The Shining in 'code', including "all blank and no blank makes blank a blank blank, " which obviously refers to the "all work and no play makes Jack a dull boy" scene from the movie. However, that scene (and the one where Danny sees the two "blanks" in the hallway) is not found in the book; only in the movie. (00:13:55)
Suggested correction: I know they're talking about the book, but doesn't it actually make sense for Joey to be referencing the movie, even though the conversation is about the book? Considering the character, I don't think that's off at all. He's read the book, but he's obviously seen the movie, too.
The One With Monica's Thunder - S7-E1
Audio problem: When Joey walks out of the bedroom dressed as a 19 year old, when Chandler says the line "Yes, on a scale from 1 to 10, 10 being the dumbest a person can look, you are definitely 19", you can see that the audio doesn't match the words. It looks as though Matthew Perry says "not 19" and they had to re-dub over post production with "19." Subtle, but it's there. (00:08:50)
Suggested correction: Just watched it twice and seems to be fine... Can't see any issue.
The One with the East German Laundry Detergent - S1-E5
Revealing mistake: When Rachel says, "If you want this cart you're gonna have to take me with it.", you can see Ross mouth "with it" behind her. (00:20:30)
Suggested correction: Ross makes a grimace with his mouth before and during the line but is not mouthing lines.
The One With All The Thanksgivings - S5-E8
Other mistake: When Joey comes out the bathroom in the girls' apartment with a turkey stuck on his head, the bathroom floor has the black and white tiles. But that floor wasn't there until Joey put it there in Series 3, The One With Frank Jr. So in the flashback the bathroom floor should be white tiles. (00:04:45)
Suggested correction: Joey said in the Frank Jr episode that the tiles used to be a different colour. The thanksgiving flashback was in 1992 so something must have happened to the bathroom floor tiles in the time gap between 2 years before the series started and three years after it did.
The One With Rachel's Other Sister - S9-E8
Revealing mistake: When Chandler grabs his bag he accidentally lets the box full of wedding china fall off the stool. Watch closely (play in slow-motion). The box falls on the floor and shattered china falls out. The china was ALREADY broken before it falls on the ground. (00:23:00)
Suggested correction: Slow-mo is not permitted under this site's rules.
The One with the Dozen Lasagnas - S1-E12
Revealing mistake: After Phoebe tells Rachel that Paolo made a pass at her, we see a shot of the outside of Monica's apartment block and Rachel is throwing Paolo's clothes out of the window. Look closely and you can see the clothes have been very badly superimposed on to the background. (00:17:05)
Suggested correction: The show sent a crew to New York to film the clothes being thrown from the same building that is used in establishing shots. In a wide-screen version of the episode, the clothes can be seen being thrown out a window (although in the episode the clothes are supposedly thrown off a balcony).
The One With Joey's Porsche - S6-E5
Revealing mistake: When Phoebe knocks over the vase she glances at it just before throwing the diaper. (00:15:10)
Suggested correction: The bin for the diapers is near the vase, and she glances at that before throwing the diaper.
The One With Phoebe's Birthday Dinner - S9-E5
Continuity mistake: Rachel is telling Ross why she doesn't want to go to the dinner, and she says "the first sign is I don't want to, and...I'm not going'. While she says this, her left hand is completely empty, but then in the next shot the camera goes back to Ross and she is now holding the baby monitor in that hand. It then moves around in different shots afterwards. (00:06:10)
Suggested correction: She comes in with that baby monitor and it never leaves the sight of camera.
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)
Suggested correction: We are also shown how the Chick and Duck are in both apartments over time. And also, just because they are not shown on screen doesn't mean you can't hear them.
The One With The Ring - S6-E23
Plot hole: When Phoebe accidentally allows Chandler's ring to be sold, she tells him that she overheard which restaurant the guy said he was taking his girlfriend to, so they can go find him and persuade him to exchange rings. However, in the previous scene we see that Phoebe was paying no attention at all to that guy - she was too busy trying on jewellery. She wasn't even within earshot of the guy, and we see from her reaction that she hadn't even noticed him at all before he left the store with the ring (during which time he doesn't say anything at all). (00:16:50)
Suggested correction: She may have been trying on all the jewellery, but she would have certainly heard the guy say he was going to a certain restaurant with his girlfriend before he left. Obviously she then realised the ring the man bought was the one Chandler had his eye on so reacted.

Continuity mistake: After Chandler makes the joke about Joey cracking show business, Joey is holding the phone in his left hand. In the next shot, it is in his right hand. (00:11:20)
Suggested correction: You can actually see him switch it to the other hand before the next scene pops up if you look close enough.
Not for the shot the mistake is talking about. Throughout the scene he's switching the phone back and forth. But after Chandler's line, Joey is just standing there with the phone in his left hand, he doesn't make any move to switch hands. In the next shot, the wide shot from the side showing everyone, you see the phone is in his right hand.

The One Where Underdog Gets Away - S1-E9
Continuity mistake: At the end of the episode when Chandler makes a toast, he is holding the glass in his right hand. In the next shot, the glass has jumped to his left hand. (00:21:05)
Suggested correction: He switches the glass from right to left, so, unfortunately you're wrong.
The mistake is valid. While we do see him switching his glass between hands during the scene, when he says he's glad everyone's Thanksgiving sucked, he raises his glass in his right hand. In the next shot it's switched to his left and lowered a bit. Since this happens between shots (and he's not off camera), it means no time elapsed, so there's no time for him to switch hands again (in the submitted pictures, the bottom picture is the first shot and the top picture is the 2nd shot).
The One Where Nana Dies Twice - S1-E8
Continuity mistake: When Phoebe say 'what a great day' she starts to put her hand to her face, then in the next shot, her sunglasses have jumped to her hand. (00:14:20)
Suggested correction: You can see she takes the sunglasses off as she's speaking.
The One With The Worst Best Man Ever - S4-E22
Other mistake: Given her vegetarianism, and her disdain for fur in another episode, there's no way Phoebe would have wanted a pair of leather pants.
Suggested correction: It's your opinion that Phoebe wouldn't have wanted leather pants, but that's not true of all vegetarians. Natalie Merchant was known for saying she was a vegetarian but still wore leather shoes. I was a vegetarian who would never have worn fur and still wore leather shoes.
The One With Joey's Big Break - S5-E22
Other mistake: When Ross is questioning Phoebe on why she is mad at him, he has his blue sweater on backwards.
Suggested correction: So he has his sweater on backwards. That's a character mistake, not a movie mistake.
Suggested correction: I've seen a few of these listed as errors, but they're not. A lot of shows do this often if you pay attention. It's called "product displacement", and it is done to avoid being sued or having to pay licensing fees. Also, it is cheaper to alter logos like this than pixelate/blur them out. What is interesting though, is that one of the grape nut boxes in this picture does not have an altered logo.
Yes, it's product displacement, and this is specifically referred to as the "greeking" process. However, your correction only offers an excuse as to why this occurs. The tape or paint partially or fully covering the brand names or logos are a distraction, and it removes viewers from the fake reality of the show or movie. Originally, these types of submissions were to be listed in trivia, but instead they were placed in the mistake section.
Super Grover