The One Where Chandler Can't Cry - S6-E14
Continuity mistake: In the cafe, Ross says to Rachel, "I'll tell her we can't see each other any more," and we see Rachel bring her hands down from her face. However, in the previous shot we had already seen her lower her hands. (00:03:25)
The One With Joey's Award - S7-E18
Continuity mistake: When Rachel and Joey are talking, the syrup bottle moves from the label facing Rachel to the label facing the camera. (00:05:50)
Continuity mistake: On the plane, when Rachel says "She's almost never right," (about Phoebe) you can see the guy's hand is on the armrest. Then a split second later, his hand is about half a feet off the armrest while saying "But she is sometimes." (00:15:15)
Other mistake: When Ross tells Rachel he can't see her anymore, the door to Monica's room is open revealing a completely blank and empty room. (00:09:50)
The One With The Nap Partners - S7-E6
Continuity mistake: Monica and Chandler are in their apartment talking about Monica's worries that Chandler would dump her if she put on weight. When we first see Monica, the bite mark in her apple is quite small, but a few seconds later, it is suddenly much bigger without her eating any more of it. (00:18:00)
The One with All the Poker - S1-E18
Continuity mistake: When the group is sitting around the table in Monica's apartment playing poker, Monica is making something to eat. When she puts it on the table and sits back, we can see a pile of plates on the table on her right side. But in the next shot, the plates are gone. (00:05:35)
The One On The Last Night - S6-E6
Continuity mistake: At the end when Monica and Chandler hug, Monica's arms keep going from under to over Chandler's arms as the cameras switch many times. (00:20:00)
The One With Rachel's Phone Number - S9-E9
Continuity mistake: In the scene where Joey is sitting in front of his door with the baseball bat, the bar stool is directly in front of his door. When he stands up the chair does not move. However when he and Chandler come back to the hall the chair is over in the corner next to his door. (00:16:00 - 00:19:35)
The One Where Underdog Gets Away - S1-E9
Visible crew/equipment: When Monica shuts the TV off while watching skiing, there is a closeup of the screen as it goes blank. You can see reflected in the blank screen an image of a man in a long sleeved shirt and tie, who does not correspond to any of the characters in the room. (00:08:00)
The One That Could Have Been, part 1 - S6-E15
Continuity mistake: Near the start, Chandler is sitting in the coffee house in the big chair. When he's talking to Joey about money, his feet change positions every two seconds. On the floor, crossed, resting on the table, the list goes on and on. (00:04:55)
Continuity mistake: When Chandler and Monica are in the birthing room and they have just been told they are having twins, her scarf keeps changing from sitting on her shoulder to being over her shoulder. (00:10:20)
The One Where the Monkey Gets Away - S1-E19
Continuity mistake: When Monica looks at Barry and Mindy's engagement notice in the magazine, she folds the page over. In the next shot, the magazine is open in her hands. (00:01:50)
The One with Two Parts: Part 1 - S1-E16
Visible crew/equipment: At the Lamaze class just before Ross and Susan argue about who should lie on the floor, a boom mic can be seen in the top left corner of the screen. (00:08:50)
The One with the Stoned Guy - S1-E15
Continuity mistake: After Chandler walks in on Ross and Joey talking dirty, Ross is holding his right hand up as he and Joey start to explain to Chandler. In the next shot his arm is by his side. (00:13:10)
The One with the Candy Hearts - S1-E14
Continuity mistake: Just before Carol and Susan enter the restaurant, Ross reaches for the menu with his left hand and his right hand is under the table. In the next shot his right hand is holding onto a cup on the table. (00:11:20)
The One With Rachel's Date - S8-E5
Visible crew/equipment: When we see Central Perk for the first time, you can see a stage light is reflected in the window. (00:05:20)
Continuity mistake: When Joey and Chandler are discussing Joey's shoes, the length of the sleeve round Joey's neck changes depending on the shot. (00:11:20)
Continuity mistake: When Monica and Rachel are discussing Phoebe, Rachel's hands go from playing with the table to dry washing depending on the shot. (00:12:30)
The One With Joey's Big Break - S5-E22
Continuity mistake: When Rachel knocks over the cereal its position changes between shots. (00:04:15)
The One In Barbados, part 2 - S9-E24
Continuity mistake: At the end of the episode, when Joey walks into Rachel's hotel room, he is standing in the doorway. However, when Joey and Rachel kiss, there is enough space for the door to close. (00:47:05)
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.