The One With The Rumor - S8-E9
Continuity mistake: In the episode with Brad Pitt in it, when Ross and Will are standing by the fridge and Rachel comes in, Will's right hand jumps around after he crushes the decoration on the wall. (00:08:40)
The One with Two Parts: Part 1 - S1-E16
Continuity mistake: At the start of the episode, Chandler is holding onto a menu with his right hand. In the next shot, it is gone. (00:00:10)
The One With Joey's Dirty Day - S4-E14
Continuity mistake: When Rachel is asking Ross if he will take Emily to the opera, the amount of biscuit in his hand changes throughout. (00:06:15)
The One With The Screamer - S3-E22
Continuity mistake: When Gunther brings Chandler the cup of coffee from the woman at the bar, Chandler does not take it by the handle; however the shot quickly switches to him holding it by the handle. (00:14:00)
The One With The Video Tape - S8-E4
Continuity mistake: When Rachel has the tape and is explaining why she wants to watch it, she is holding it in her left hand with her right hand on her chest, when the shot changes to behind her, she has it in her right hand. (00:15:30)
The One With The Hypnosis Tape - S3-E18
Continuity mistake: In the diner scene, Rachel makes the comment about working in fashion and straight men, and her left hand is empty; in a flash, a piece of bread appears without her picking it up. (00:06:40)
The One With The Truth About London - S7-E16
Continuity mistake: After Rachel shows Ben the pencil and quarter prank, she lays the pencil down and it is pointing straight ahead. When the pencil is shown again it has moved. (00:05:45)
The One Where Rachel Goes Back To Work - S9-E11
Continuity mistake: Ross bends over Emma to kiss her and gets the bow stuck on his head. The bow is slightly over his left eye but in the next shot, it has moved to the centre of his forehead. (00:11:35)
Continuity mistake: When Ross and Rachel are in bed, and Rachel says she remembers laughing a lot, and Ross says "Then we didn't have sex," Rachel turns her head away from Ross twice. (00:03:10)
Continuity mistake: In this episode, they say the reason Kip was phased out was because he dated Monica and they broke up badly. However, in the first season (in the "Dozen Lasagnes" episode) Chandler says Kip left because he got married. (00:13:50)
Continuity mistake: Ross, Joey and Chandler are in Chandler and Joey's appartment talking about Ross' decision. Chandler has a green bottle in his hand. He puts it down behind the computer by the microwave, but when Ross starts listing Rachel's "cons" the bottle's suddenly at the opposite end of the counter. (00:07:40 - 00:08:25)
The One with the Stoned Guy - S1-E15
Continuity mistake: When the stoned guy says they should make macaroni and cheese, Monica holds out her hands. In the next shot, her hands are clasped together. (00:18:50)
The One With The Video Tape - S8-E4
Continuity mistake: As Joey says thanks to Ross for his offer to help him if he has a problem with the ladies, he puts his hand on Ross's arm. Camera cuts and it is by his side with no time to move it. (00:11:35)
The One Where Rachel Tells... - S8-E3
Continuity mistake: When Joey finds out condoms are only 97% effective, he has his arms crossed. The camera changes angle and he now has them by his side. (00:14:30)
Continuity mistake: When Rachel spits out the champagne for the first time, her necklace is center chest. When the camera cuts it is far right. (00:13:25)
The One With The Halloween Party - S8-E6
Continuity mistake: The amount of carrot Chandler has keeps changing from less to more. (00:10:35)
The One With Monica and Chandler's Wedding, Part 1 - S7-E23
Continuity mistake: When Monica is talking to Chandler about nothing having gone wrong, Chandler's arms are crossed. The camera cuts, and his arms are down by his side. (00:06:50)
Continuity mistake: When Rachel is talking to Phoebe about cremating the coat there is a mirror behind her with a laptop reflected in it. The reflection shows it switched on, but in the wider shots it is switched off. (00:09:15)
The One Where Ross Dates a Student - S6-E18
Continuity mistake: When Chandler, Joey and Ross are talking about Donna Keystone from college, Ross is holding a water bottle; it disappears, then he is holding it again. (00:13:15)
The One with the Monkey - S1-E10
Continuity mistake: When Rachel says about her 6th date with Paulo, she is holding a decoration for the tree. In the next shot the decoration changes to a much larger object. Then, in the next shot, as she hands it to Monica, it has turned back to the original shape. (00:05:40)
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.