The One With The Routine - S6-E10
Continuity mistake: When the Snippy Guy is pointing out couples to go on the platforms next, he points to one couple with his left hand, while holding a clipboard in his right hand. In the very next shot he points to the next couple, but this time with his right hand while holding the clipboard in his left. (00:11:15)
Other mistake: In 'The One with the Ick Factor' (Season One) Monica states that she is 26 years old. This episode takes place in 1994/95. However there are numerous other episodes such as 'The One With All The Thanksgivings' that show Monica and Rachel (who are the same age and in the same class) still being in High School in 1988. In 'The One Where The Stripper Cries' the two have to sneak into a college party in 1987 as they are still high school age. They should be at least 19 or 20 in 1987/88.
Continuity mistake: When Phoebe is talking to her stalker for the first time, at one point, he tips the flowers to the side when Phoebe says, 'Well, this is awkward,' and he puts his left hand on the end of the stems. In the next shot he is holding them with both hands. (00:02:55)
The One With Joey's New Brain - S7-E15
Other mistake: In the scene where Phoebe and Rachel are talking in Phoebe's apartment and Tom is waiting at the door, after Phoebe says "you are such a good friend", we hear someone say Tom, meaning its Tom's turn to talk. Extended episode only. (00:20:55)
The One With Joey's Award - S7-E18
Continuity mistake: When Rachel walks in on Joey with the syrup bottle, he sets it down. In the next shot, he is holding it again. (00:05:10)
The One With The Apothecary Table - S6-E11
Continuity mistake: In the very first scene when Janine and Joey are kissing at the table in Central Perk, the blue cup by Joey's arm moves forward a few inches without him touching it. (00:01:25)
The One With Ross's Teeth - S6-E8
Revealing mistake: When Ross's date turns the lights down he can speak and yet the whiteness of his teeth doesn't show. (00:17:25)
Continuity mistake: When the group is in the coffee house discussing Kip there is a bag on the table in front of Monica. When Rachel enters she places her bag on top of the bag already sitting there. Toward the end of this scene Rachel's bag then disappears and only the original bag is now sitting there. (00:13:10)
The One With Barry & Mindy's Wedding - S2-E24
Audio problem: When Rachel asks Barry and Mindy why people keep telling her to 'get well soon' and Barry says his parents told everyone she has syphilis, and in the next shot it shows Rachel trying to take this information in, Barry seems to still be talking, but no sound is coming out of his mouth. (00:09:25)
The One with the Dozen Lasagnas - S1-E12
Revealing mistake: When Rachel throws Paulo's clothes over the balcony, they land on the corner of the building, yet the balcony isn't near the corner as there are bedrooms between the place where she throws them and the edge of the building. (00:17:15)
The One With The Ball - S5-E21
Visible crew/equipment: A cameraman can be seen in the TV when Rachel is on about the cat she had as a kid. (00:04:25)
The One With The Inappropriate Sister - S5-E10
Visible crew/equipment: When Ross and Monica are wrestling, the stagelights can be seen in the tv. (00:12:45)
The One With All The Rugby - S4-E15
Continuity mistake: When Rachel is talking to Joey about flushing the toilet, her hands go from counter to bottle top to counter with no time between camera cuts. (00:02:00)
The One Where Chandler Takes a Bath - S8-E13
Continuity mistake: When Chandler takes hold of the boat he grabs the middle of it, the camera changes angle and he is now holding it at the end of the boat. (00:06:20)
The One Where Ross Dates a Student - S6-E18
Continuity mistake: When Rachel and Joey are at Joey's apartment throwing wet paper towels at the entertainment unit, Phoebe comes in to ask Rachel to switch back to Monica's apartment. During the scene, Phoebe is standing in front of the entertainment unit, and the wet paper towels' number and positions change between shots. (00:18:10)
The One With The Dollhouse - S3-E20
Continuity mistake: When Joey is talking to the understudy, he is holding a cup. It disappears right when she invites him for a drink. (00:07:20)
The One With Ross's Grant - S10-E6
Visible crew/equipment: When Joey turns the video off, the end of the set is visible in the TV. (00:15:10)
The One Where Joey Tells Rachel - S8-E16
Continuity mistake: When Monica is talking to Ross about how Joey feels, there is a shot of Monica bending down to talk to Ross, and some magazines on a table. At the end of the scene the magazines have changed place. (00:05:30)
The One with George Stephanopoulos - S1-E4
Continuity mistake: When Phoebe talks about the cave in in the mine, Ross has his hands in his pocket behind her. In the next shot his hand is on the sofa. (00:04:10)
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.