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.
The One With Chandler's Dad - S7-E22
Continuity mistake: When Monica receives her gift from his father, the Porsche, it's gray. When Rachel takes the keys from Ross' jacket and gets into the car in this episode, the Porsche is black. (00:04:49)
The One With The Free Porn - S4-E17
Continuity mistake: Near the end, when Emily walks into the house, the TV should be on with the porn. But instead, it's turned off.
The One With The Blind Dates - S9-E14
Continuity mistake: When Ross and Rachel are at the coffee shop after their dates, Rachel's necklace disappears and reappears twice. (00:20:20)
The One Where Monica Gets a Roommate - S1-E1
Continuity mistake: When Ross shows Chandler and Joey the can of "Carol's favorite beer" it's unopened as Ross makes a crack about how he "should have known," but in the next shot we see Ross lifting the can and drinking from it, even though he never actually pulled open the stay-tab between the two shots (viewed in widescreen). [In the extended version of the episode you see Ross open the can before taking a drink. In the standard version, the mistake is valid]. (00:09:55)
The One With The Giant Poking Device - S3-E8
Visible crew/equipment: Right after the intro, in the first shot of Gunther, Ross, and Rachel, just as Ross says, "Thanks, Gunther," the camera is visible at the left side of the screen. (00:02:00)
The One With The Proposal, part 1 - S6-E24
Factual error: There's no charity event in the world that would be clamoring for non-paying guests and offering them free food and an open bar.
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.
The One Where Joey Moves Out - S2-E16
Other mistake: When Rachel is showing Phoebe her heart tattoo, the tattoo isn't dressed and covered, nor is the skin around it red or swollen, despite the fact she just finished getting it. (00:14:09)
The One Where Joey Dates Rachel - S8-E12
Factual error: When Chandler is explaining that he played Ms. Pac Man all day, the Ms. Pac Man machine is unplugged, and then plugged back in. Immediately upon being plugged back in, we hear the Ms. Pac Man theme song being played. No version of a Ms. Pac Man stand-up arcade ever played the theme song upon powering on. Instead, it would silently go into "demo mode." The only way the stand-up arcade version of Ms. Pac Man would ever play its theme song was after two events occurred in order: 1. A coin was dropped in the slot (or a button was pressed on the inside of the unlocked coin drawer), and then 2. Someone pressed the '1 player' or '2 players' button to start the game. It is clear that neither of these things has happened in the scene by the time the music starts playing. (00:11:50)
The One With Mac & C.H.E.E.S.E. - S6-E20
Continuity mistake: In the episode before, Rachel's hair is just underneath her shoulders. Then, a few weeks later when Ross gets back from Spring Break, it's a lot longer than before.
The One Where Rachel Tells... - S8-E3
Visible crew/equipment: When Monica is yelling at the other couple on their honeymoon, the things on the shelves behind them shows the reflections of set lights. (00:15:25)
The One Where Old Yeller Dies - S2-E20
Continuity mistake: A woman and a man in a blue shirt exit the coffee shop twice.
The One With The Bullies - S2-E21
Continuity mistake: A woman and a man in a blue shirt exit the coffee shop twice.
