The One With Chandler's Dad - S7-E22
Continuity mistake: When Monica and Chandler are in Vegas waiting for the show to start, Monica's wrap goes from high up on her shoulders to half way down her upper arms between shots. This happens more than once. (00:12:40)
The One With The Dollhouse - S3-E20
Continuity mistake: After Joey walks away from the understudy and sits at the table, his hands are on the table but not touching; they are touching in the next shot. (00:07:50)
The One With the Sharks - S9-E4
Continuity mistake: When Chandler and Monica are talking about Chandler's shark obsession, his arms keep changing with each shot. When the shot is from behind (facing Monica) they are on the couch, and when the shot is in front (facing Chandler), his arms are folded in front of him. (00:19:35)
The One In Vegas, Part 1 - S5-E23
Continuity mistake: Chandler comes down to find Monica and sees that she's playing some game and having fun. He makes a sad and dejected face. The scene cuts back to Monica, and then to the exact same shot again of Chandler making the sad and dejected face. (00:22:00)
The One with the Thumb - S1-E3
Continuity mistake: After Chandler shouts at everyone because they are complaining about his smoking, there is an awkward silence and we see a shot of Rachel leaning on the sofa with her arms spread. In the next shot she isn't leaning on the sofa anymore. (00:14:25)
The One With The Ballroom Dancing - S4-E4
Other mistake: In the scene where Rachel is going to take out the trash, Monica tells her the garbage room is the 3rd door on the left. However, when Rachel comes back with the pizza box and Monica leaves for the garbage room, she leaves the apartment and walks towards the right - there are no doors that way, just the stairs. (00:00:50)
The One Where Ross And Rachel Take A Break - S3-E15
Continuity mistake: When Phoebe and Monica are at Monica's table and Phoebe is trying to convince Monica to go on a date with her date's translator, watch Phoebe's arm. She points at Monica when she says, "Don't call him that; his name is Spackleback Larry", but when the shot changes to a side view of them, she has her arm resting on the table with no time to put it down between shots. (00:06:25)
The One With Joey's Porsche - S6-E5
Continuity mistake: Phoebe knocks over a vase and has to clean it up because "Let's face it; we're at Monica's." When she turns back around and notices one of the babies is missing, the baby on the right (in the striped top) falls over towards the other baby. A split second later when the shot changes the baby is sitting upright again. (00:15:15)
The One With The Ball - S5-E21
Visible crew/equipment: A stage light can be seen above Ross when he asks Rachel how much she paid for her cat. (00:04:05)
The One With Chandler In A Box - S4-E8
Continuity mistake: In the scene were Phoebe is calling for Monica's eye doctor, in the background you can see the TV is off. Then Phoebe asks if she wants to see the on call doctor, Monica says yes, and in the background the TV is on. (00:03:55)
The One Where Rachel Tells... - S8-E3
Continuity mistake: In the deleted scene on the DVDs Chandler is leaving the security interview with his holdall over his shoulder by the short strap. The camera cuts to outside the room and the holdall is now level with his legs. (Mistakes in Deleted scenes are valid if they are only in that scene which this is.) (00:24:50)
The One Where Rachel Tells... - S8-E3
Continuity mistake: In the deleted scene on the DVD, Chandler puts his plane tickets in his shirt pocket. Next shot the tickets have reversed. Look at the blue section. (Mistakes in deleted scenes are allowed if they are in that scene.) (00:25:00)
The One with the Stoned Guy - S1-E15
Continuity mistake: When Phoebe asks Chandler if he wants to be a chef, Monica says 'Hi, there' with her right hand raised. In the next shot, it is on her lap. (00:03:05)
The One with Two Parts: Part 1 - S1-E16
Visible crew/equipment: In Central Perk when Ross realises he's going to be a father, a black and white boom mic can be seen at the top of the screen. (00:16:50)
The One With Ross's Sandwich - S5-E9
Continuity mistake: When Ross is in Central Perk talking about his day at work and how he is not going to work for a while because of his rage, watch his cotton candy. It changes in sizes and shape a lot, from big and uncircular to small and circular. (00:14:50)
Continuity mistake: When Chandler and Monica are at the hospital holding the twins right before they try and swap babies, there are two hospital tags around Chandler's left wrist which then disappear before re-appearing. (00:15:25)
The One Where No One Proposes - S9-E1
Revealing mistake: When Rachel is breastfeeding Emma for the first time, the baby's head is constantly moving in the same repetitive pattern suggesting it is one of those life-like dolls. Babies do not move their heads like that. (00:08:20)
Continuity mistake: When Ross and Rachel are standing at Ross' door after Rachel comes over to say goodbye and they are hugging and talking, Ross' right hand changes from being on Rachel's shoulder to on her waist and then back to her shoulder. (00:00:35)
The One With the Baby on the Bus - S2-E6
Continuity mistake: When Rachel is introducing the "professional musician" in Central Perk, just as she walks off a bald black man in a red shirt walks past the window. Then the woman sits on her stool and the man walks past again. (00:13:50)
The One With All The Kissing - S5-E2
Continuity mistake: In The One With All The Kissing, Phoebe grabs a photo of the other 5 by the Tower of London. When we see a shot of her a few seconds later drawing herself into the photo, it's a different photograph. (00:07:25)
Answer: Usually by the seventh night of Hanukkah you don't know what to get the other person, and you will probably resort to getting the other person something insignificant. Chandler is basically saying that the pen is a stupid gift.