The One Where Phoebe Hates PBS - S5-E4
Continuity mistake: In the opening scene where Rachel is checking the mail and is walking over to Monica's room, she has a pair of pumps on, then once she has walked in on Monica and Monica runs after her to say she was taking a nap, Rachel is wearing a pair of backless high-heeled sandals, then when Joey and Ross come in, Rachel is wearing the pumps again (we see this when Ross says "I had to talk loud because the movie was loud"). (00:00:10)
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)
Plot hole: In TOW Ross tells Rachel he cannot see her following a promise to Emily, the rest of the friends go into Monica's bedroom. Joey hauls out a box from under the bed, saying that he's been hiding it there since Ross said the wrong name at the wedding. Surely Monica, with her obsession for keeping the place clean, would have noticed a box under her bed? (00:04:10)
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)
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)
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: Rachel and Phoebe are in the Central Perk, talking about leaving the group, and a jacket and a handbag are hanging on the arm of the chair behind Rachel, slightly to her left. Between shots it changes from just the jacket, then just the handbag and so on. This continues throughout the scene when Ross comes in and Phoebe leaves. As she gets up you see both again, however Rachel does not move enough to just show one and hide the other. (00:16:00)
Continuity mistake: In the beginning of the episode Chandler opens the door to the bathroom and Joey is sitting on the toilet. This is the only episode the toilet is positioned there. It is normally behind the door in other episodes.
Audio problem: When Rachel and Ross are in Central Perk, Ross says "Well there's this one thing." Then it cuts to a shot of the side of his head where he says "Okay" and it doesn't match his lips.
Revealing mistake: When Monica and Rachel apologise to Danny, as he shuts his door for the second time the set wall visibly shakes. (00:07:55)
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)
Continuity mistake: Ross is in his apartment, and he is saying he will miss it. Throughout the scene, the phone appears and disappears from beside the charger cradle. (00:10:10)
Visible crew/equipment: When Ross notices that Ugly Naked Guy is back, in the next exterior shot we can see the top of the set as everyone gathers at the window.
Visible crew/equipment: While everyone's in the apartment Ross is on the balcony talking to Emily on the phone, and in the mirror we can see the reflections of Phoebe and someone else wearing a blue shirt (with a large white pattern) and blue pants (looks like jeans), but none of the others are actually dressed like that.
Visible crew/equipment: Just as Monica and Rachel walk into the storage room, at the start of the shot the camera casts a shadow on the head sculpture which moves as the camera moves.
Continuity mistake: When Rachel and Monica knock on Danny's door and he opens it, there is a wall a few feet behind him. Later, when Rachel shows up at Danny's apartment to cancel their date, she enters into an open room and there is no longer a wall in front of the door. Danny's apartment is supposed to be one floor directly below Chandler and Joey's apartment. This was obviously the same set for their apartment that was used for Danny's and the wall was added for that shot to disguise it.
Continuity mistake: Joey's bedroom door opens and closes as the camera goes between him and Monica and Chandler when he is telling him he doesn't want to see them kissing.
The One Where Ross Moves In - S5-E7
Continuity mistake: At the very start of the episode, when Joey's showing Chandler National Geographic, Chandler has his left hand up by his face in one shot, then when the angle changes they're both clasped in his lap. (00:00:05)
The One Where Ross Moves In - S5-E7
Continuity mistake: Chandler and Joey are on their couch thinking about what to do about Ross; when Chandler says "what are we gonna do?", he switches from crossed arms to hands folded in his lap. (00:15:45)
The One Where Ross Moves In - S5-E7
Continuity mistake: When Chandler and Joey walk into the apartment to find boxes all over the place and also when Chandler talks about the air purifier, the door to the bathroom is open and the toilet is right beside the tub (odd that it's there in the first place), but when Joey tells Chandler he wants to play foosball and also when Joey's wearing the helmet, the prop toilet has vanished.
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.