The One With the Male Nanny - S9-E6
Continuity mistake: Towards the end, during a scene at Ross and Rachel's, Sandy picks up two puppets and puts them on each hand. He starts pulling the blue one onto his left hand, but when the angle changes there's a yellow one on his left hand, and a blue one on his right. It cuts to Ross, then when we go back to Sandy they've changed hands again. (00:24:30)
The One With Joey's Award - S7-E18
Continuity mistake: When taking Jessica's award, Rachel opens the door. But when the camera cuts, Joey is first through the door. (00:18:40)
The One Where No One Proposes - S9-E1
Continuity mistake: In the scene where Rachel believes Joey has proposed to her at the hospital after having Emma. Ross is talking to Rachel about her saying yes to Joey's proposal. The nurse brings Emma in to breast feed. When the nurse leaves, she closes the door. However, when they shoot back to Joey a couple of times before he leaves the room, the door is open. (00:19:45)
Revealing mistake: In the one after Monica and Chandler get married, Chandler says he can't dance because his shoes are slippery. If you look closely, he managed to slip so much by standing on the bottom of Monica's dress, not because of the shoes. (00:06:00)
The One With The Rumor - S8-E9
Continuity mistake: The gang confronts Ross over his affair with a fifty-year old librarian when he was younger. If you watch the mirror behind him (in one of the girls' rooms), it changes angles every time the camera cuts between Ross and the rest of the gang. (00:17:40)
The One With All The Thanksgivings - S5-E8
Continuity mistake: When Phoebe's trying to make the TV work at the beginning, in the close-ups and the first wide shot the remote's at an angle, but in the second wide shot it's straight. It then goes back to being at an angle. (00:00:15)
The One With Ross's Sandwich - S5-E9
Continuity mistake: In Central Perk, when Phoebe writes a note for Ross to put on his sandwich so no one eats it, she mentions that she stabbed a cop, and has a green mug in her hand. It cuts to Monica then back to Phoebe and the mug is out of her hand and she's yelling, "He stabbed me first." When it cuts back to the wide shot the mug is back in Phoebe's hand. (00:05:40)
The One With The Hypnosis Tape - S3-E18
Visible crew/equipment: When Monica leaves the apartment and everyone is watching you can see the stage lights on the ceiling in shots from Pete's viewpoint. (00:18:10)
The One Where Eddie Won't Go - S2-E19
Continuity mistake: When Eddie leaves Chandler's room, you can see it's not the living area. (00:01:10)
The One Where Rachel Has a Baby, part 1 - S8-E23
Continuity mistake: When the couple who has bad pet names for each other is sharing the maternity room with Rachel, the man is unpacking a suitcase that he closes, but in the next shot its open and he flips the top closed again. (00:09:10)
The One With Ross' New Girlfriend - S2-E1
Continuity mistake: At the beginning when Rachel falls and starts bleeding, you can see that the wound is somewhere up above her forehead because the blood is running from the wound up there. However, throughout the rest of the episode she has a bandaid going horizontally across her forehead, nowhere near where the apparent wound was. (00:01:20)
The One Where Estelle Dies - S10-E15
Continuity mistake: Near the end when Chandler is talking to Janice at one point his hands go from pointing straight ahead to his pockets. (00:17:20)
The One with the Blackout - S1-E7
Continuity mistake: In the scene where Joey is standing with candelight over Ross' neck, the candle is full length, but in the next shot it's only half length. (00:13:00)
Continuity mistake: In the scene just before Joey goes into the shower, when he is thanking the director for the opportunity, the camera shot goes back and forth between Joey and the director several times. During this series of shots, the part in Joey's hair switches sides nearly every time. It appears that the entire shot is reversed - in the closeup, the shower curtain is on his left and the shadow to his right is sharply focused. In the lower (long) shot, the curtain is to his right, and the shadow on his left is more focused. (00:13:05)
The One With Rachel's Inadvertent Kiss - S5-E17
Revealing mistake: When Ross is doing his "Watching TV" bit, there is a brief shot of the blank screen that he is sitting on the sofa pretending to watch. In the screen's reflection, it is clear that the sofa is empty. (00:03:55)
The One Where Phoebe Hates PBS - S5-E4
Continuity mistake: Monica comes to get her pan back from Chandler, and when she opens the door, the magna doodle pen is hanging down. The shot changes and it is attached to the board; it changes again and it is hanging once more. (00:12:00)
The One Where Underdog Gets Away - S1-E9
Revealing mistake: Whenever Monica's apartment is shot from the point of view of the balcony looking in, fake walls have to be put up across the room to cover the open space (since there is no wall there usually). When the friends are looking out the window at Ugly Naked Guy and his girlfriend in this episode, you can see that the rear wall does not extend nearly far enough - there is a large black space behind Monica. (00:19:25)
The One Where Rachel Finds Out - S1-E24
Visible crew/equipment: When Rachel is on the balcony with her date, after she kisses Ross and says, "Wow!", the shot changes back to her date. While he is saying, "Exactly" you can see a camera man on the left side of the screen. Then when the shot changes to show Rachel and her date you can see him move out of the shot. (00:19:45)
The One With Phoebe's Husband - S2-E4
Continuity mistake: In the scene where Rachel is telling Ross it is sexy for a man to wait before having sex, the cups behind Ross change color: red to green to red and back again. (00:08:10)
The One With Ross's Sandwich - S5-E9
Continuity mistake: In the scene where Joey has just brought home his date, he jiggles the door handle, which makes Monica and Chandler run off into Chandler's room. Chandler kicks a circle cushion off the mat, but when the camera cuts back, it's on the mat again, and then off the mat again when Rachel walks in. A red cushion also moves. (00:09:10)
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.