Continuity mistake: In season 1 ("The One with George Stephanopoulos") the date's October 20th, and Ross says his birthday "was 7 months ago". In season 4 ("The One With Joey's New Girlfriend") Gunther is pretending to collect birthdays, and Ross starts saying "mine's December the..." before being cut off. In season 9 ("The One Where Emma Cries") Ross says his is on October 18th. (00:15:10)
The One With The Hypnosis Tape - S3-E18
Factual error: When Pete takes Monica to Rome for the date this would have been impossible as Rome is 6 hours ahead of New York and at least 4/5 hours travel time, assuming they went by Concorde (double that otherwise). They would have had to have left New York early in the morning to make dinner for 8/9 pm in Rome.
The One With The Mugging - S9-E15
Continuity mistake: When Joey goes to Monica and Chandler's apartment, he goes to the fridge to get something to drink to keep his bladder full for the audition. When he closes the fridge he has two bottles in his left hand. The camera cuts to Monica, then cuts back to Joey. He then has two cans in his left hand and is holding them differently. (00:14:55)
The One Where Ross and Rachel...You Know - S2-E15
Visible crew/equipment: At the start, when Chandler and Joey sink into their new Barcaloungers and proceed to recline, the camera can be seen at the right side of the screen. This can also be seen in the show's intro in later episodes. Additionally, set lighting was reflected on the TV screen earlier when Chandler had mentioned "Green Acres."
The One With All The Rugby - S4-E15
Factual error: Rugby starts with a kickoff and not with a scrum, only the forwards on the team participate in the scrum not the whole team, and there is no scrum half to retrieve the ball from the scrum. The scrum took far too long. There is no structure to the scrum like there should be (props, locks, flankers etc). He doesn't seem to have a team and for some reason everyone just jumps on him, there is no line with one team and another it just seems like a free for all which is nothing like rugby, rugby halves are ended when the ball goes out of play which does not happen here - he just decides to end it for no real reason. Several fouls are committed in the ruck such as coming in from the sides, diving off their feet and holding onto the ball which aren't being penalised. You're not allowed to kick people or harm them intentionally in rugby, there are no cups in rugby but there are mouth guards, which no one is wearing.
The One Where Joey Speaks French - S10-E13
Visible crew/equipment: After Rachel tells the others that her father had a heart attack and Ross takes two of Monica's cookies, when it cuts to the shot of Central Perk it's from a low angle, and the studio lighting rigs at the ceiling can be seen through the windows.
The One With The 'Cuffs - S4-E3
Visible crew/equipment: While Joey's scraping gum from underneath the table there's a knock at the door, and when he gets up to head to the door the end of the set wall can be seen at the right side of the screen.
The One With Joey's Fridge - S6-E19
Visible crew/equipment: After Ross nervously sputters Professor Friesen's name as "Fee-sen-stin-linder" when he walks in on Ross with Elizabeth, it then cuts to Ross, Chandler, and Joey walking into Joey's apartment, and we can see the opening in the wall where the bulletin board usually hangs.
The One In Vegas, Part 2 - S5-E24
Visible crew/equipment: At the start of the Netflix version, when the recap scenes from 5x23 Part 1 are being shown, in the shot of Phoebe, Monica, and Chandler on the airplane the end of the cabin set can be seen beside Chandler, at the right side of the screen.
The One In Vegas, Part 1 - S5-E23
Visible crew/equipment: While Phoebe, Monica, and Chandler are with gladiator Joey in the casino, Joey notices the tension between Chandler and Monica, and when he asks what's going on a tape mark can be seen on the floor at the feet of the extra standing at the slot machine, then more tape marks can be seen at the same spot after Monica sarcastically wishes Chandler happy anniversary.
The One With The Flashback - S3-E6
Visible crew/equipment: While Joey's moving into the apartment he gets a little head rush so Monica blames the heat, and just as Monica says that it's the humidity, we can see a crew member with straight light brown hair moving around behind the open door, inside Monica's apartment - and we know it's not Phoebe or Rachel.
The One With The Mugging - S9-E15
Visible crew/equipment: When Chandler first walks into the conference room at work, and also later when he walks out of the conference room while using a cane, the end of the set wall can be seen at the left side of the screen.
The One With The Video Tape - S8-E4
Visible crew/equipment: After Rachel puts the videotape in the VCR, when she uses the remote to hit play it cuts to a closeup of the TV, and before the tape starts playing we can see the reflection of the camera dolly and a crew member wearing a white shirt, kneeling on the floor.
The One With The Routine - S6-E10
Audio problem: When Ross has finished telling everyone the story of the dreidel, we cut to Monica and Chandler's reaction shot which shows Ross' mouth moving even though he is not talking. (00:01:30)
The One In Massapequa - S8-E18
Revealing mistake: During Jack and Judy Geller's party, there are many shots where Elliott Gould's (Jack Geller) stand-in is perfectly visible. First, when Catherine walks over to offer congratulations to Rachel and Ross. Second, when Ross looks directly at his "dad" to ask if they have to pretend they're married. Then, numerous wide shots of "stand-in Jack" and Judy seated together in the background, such as after Rachel mentions the ring being the size of her fist, and during the toasts, etc. (00:06:00)
Other mistake: When Phoebe breaks into the other Phoebe's house, after she mentions that the man on the picture is "Chuck Mangionne" the door behind her opens by itself. (00:19:40)
The One With All The Wedding Dresses - S4-E20
Continuity mistake: Ross comes into Chandler and Joey's apartment to ask the guys and Rachel what they are doing in four weeks, the Magna Doodle behind him first says "poop", then its screen is blank. We cut to Joey checking his diary, cut back to Ross, and it now has "get out" written on it. [Fullscreen version]. (00:10:35)
The One Where Monica Gets a Roommate - S1-E1
Other mistake: When Rachel arrives at Central Perk, Monica introduces her to everybody, including to Chandler, as if they don't know each other. In later episodes, we learn that Chandler met Monica and Rachel a couple of times when they were in high school (including when Monica cut his toe off). Chandler even kissed Rachel once, and since Chandler always says that he hasn't kissed many women, he should have perfectly remembered Rachel, and Monica should have remembered that the two of them knew each other. (00:04:40)
Suggested correction: Chandler and Rachel never really knew each other well. Chandler will have been in her mind as that guy that her best friend's brother hangs out with, and Chandler will only know her as the friend of his friend's sister. I doubt they'd remember each other as the kiss they shared was when she was drunk, and they didn't see each other for 6 years while Rachel lived a richer and dependent on her father type life.
The One Where Old Yeller Dies - S2-E20
Visible crew/equipment: Chandler and Joey are spending time with Richard; as they play foosball and Richard scores, he leans back and says "Could that shot BE any prettier?" in a mockery of Chandler. The end of the wall and the hallway behind it are visible (ie the wall set ends). (00:16:00)
The One With The Red Sweater - S8-E2
Continuity mistake: Monica is sitting in the living room with all her wedding presents, waiting for Chandler to return. She begins to open a large parcel and reveals a brown cardboard box. Then the camera moves to Joey, and when it moves back, the parcel is wrapped up again. This happens about three times. (00:05:05)
