The One With The Secret Closet - S8-E14
Continuity mistake: In the scene where Rachel comes in to have Joey feel her stomach, he gets up from the bed and you can see the boxer shorts he is wearing. You can also see them at the end of the scene, even though he is supposed to be naked. (00:03:00)
The One With Phoebe's Dad - S2-E9
Continuity mistake: In the scene where Monica and Ross walk in carrying a few carrier bags, Monica takes out a pack of green plates, but in the next shot she is holding 4 packs of plates - 2 green, 2 red. She did not have time to pick up another pack between shots. (00:08:05)
The One With All The Kissing - S5-E2
Continuity mistake: In the Central Perk scene where Rachel is telling Ross she loves him, Ross is sitting at the small round table. The blue cup and the white cup with the lid move positions throughout the scene. (00:16:25)
The One With Rachel's Big Kiss - S7-E20
Continuity mistake: When Melissa and Rachel are first reunited at the Central Perk, the way they hold their arms (crossed, hands on hips, etc.) changes with almost every shot. (00:00:45)
The One Where Emma Cries - S9-E2
Revealing mistake: When Emma starts crying and Rachel picks her up, look at how much the baby is moving when she takes it out of the cot. In the next shot it's suddenly only moving it's head, and very slowly at that. This is because it's a robot - and it's very obvious. (00:06:10)
The One with the Sonogram at the End - S1-E2
Continuity mistake: At the start of the episode when Chandler is talking about Pink Floyd, his legs are both on the table. When the shot changes, his right leg is resting on his left knee. (00:00:50)
The One Where Joey Moves Out - S2-E16
Visible crew/equipment: When Monica, Richard, and Ross arrive at the party, the boom mike is seen at the top of the screen. (00:03:50)
The One With The Stripper - S8-E8
Continuity mistake: When Phoebe is trying to place the stripper at the beginning, her coffee cup on the table keeps changing position. (00:00:50)
The One Where Chandler Takes a Bath - S8-E13
Continuity mistake: When Joey is talking to Chandler about London, Chandler's wedding ring keeps disappearing and reappearing. (00:03:10)
The One Where Rachel Tells... - S8-E3
Continuity mistake: When Joey and Phoebe are talking about the towel incident, Joeys arm goes from bent to straight depending on the angle. (00:03:40)
The One Where Monica Sings - S9-E13
Continuity mistake: When Rachel is talking to Gavin at Ross', her position when she's sitting changes depending on the angle. (00:14:20)
Continuity mistake: When Monica goes to the mockolate interview, at one point she says "abso...lutely." While she is saying this, the mockolate packet is in her hands, but when the shot changes, the packet is on the table. (00:06:10)
The One with the Dozen Lasagnas - S1-E12
Visible crew/equipment: When Chandler and Joey are talking about buying a table, a line of stage lights is visible in the tv. (00:07:25)
The One With Ross's Thing - S3-E23
Revealing mistake: When the car catches fire you can see that the fire is not in the car but behind the car. (00:05:00)
The One With The Ring - S6-E23
Continuity mistake: When Rachel is talking to Monica about Paul crying, just before Rachel leaves, Monica has her hair over her left shoulder; the shot cuts and she now has most of her hair over her right shoulder. (00:09:50)
The One Where Paul's The Man - S6-E22
Continuity mistake: When Monica is listening to the answering machine, the bread in the blue and white bag behind her changes position. (00:12:40)
The One With The Birthing Video - S8-E15
Continuity mistake: When Chandler tells Monica and Rachel to look up and see the baby as it is being born, Monica takes her hands off her face twice and Rachel changes to the same position twice. (00:17:00)
The One In Vegas, Part 2 - S5-E24
Continuity mistake: When Monica and Chandler find the dice under the craps table, it is at an angle so both the four and five appear up. When the camera changes to the last shot (the zoom in of them kissing) the dice is sitting flat on the floor. (00:33:35)
Continuity mistake: When Monica says she wants to dance, her hair is always changing depending on the shot. (00:21:30)
The One Where Ross Finds Out - S2-E7
Continuity mistake: When Rachel finds out that Ross and Julie are getting a cat, watch Rachel's tray. When she says "together?" she's got a towel that is flat; cut to Ross and Julie for a fraction of a second, then when it cuts back to Rachel saying "both of you?" it's now in a pyramid. (00:05:15)
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.