The One With Phoebe's Birthday Dinner - S9-E5
Continuity mistake: When Pheobe says "One really does have a stick up one's ass," the waiter's hands move from in front of him to behind his back. (00:08:05)
The One With the Male Nanny - S9-E6
Continuity mistake: When Ross says, "Not knowing when to shut up, that's my thing," the amount of pizza he has eaten changes between shots. (00:21:50)
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 the Male Nanny - S9-E6
Continuity mistake: When Ross walks in on Sandy and Joey playing the recorders, Joey puts his recorder down on the table in front of him, when Ross storms out of the room, the recorder is in a totally different position and also on the far end of the table. (00:24:55)
The One With the Male Nanny - S9-E6
Continuity mistake: When Ross storms into the kitchen, exasperated by Sandy, he is immediately followed by Rachel - but she had just been holding Emma, and there wasn't enough time for her to have given Emma to Sandy before storming into the kitchen. (00:25:00)
The One With the Male Nanny - S9-E6
Continuity mistake: In The One With the Male Nanny in series nine, near the end of the episode Ross gets a beer when he is argung with Rachel as to whether they should fire him. During shots, the label on the bottle moves round. (00:25:05)
The One With the Male Nanny - S9-E6
Continuity mistake: The hallway outside Ross' new apartment (series 6 onwards) always changes. Sometimes, the apartment is at the end of a dead-end corridor, and there is a plant outside, covering up the wall; sometimes you can go past the apartment and turn left or right; or, as in this episode, you can only turn right immediately after you have passed the apartment. (00:26:00)
The One With the Male Nanny - S9-E6
Continuity mistake: When Mike and Phoebe are at Central Perk, Mike pulls his apartment key out of his pocket and he's holding the head of the key with the shank side up, but next shot he's holding the shank with the head side up.
The One With the Male Nanny - S9-E6
Continuity mistake: When Phoebe is trying to explain to David that she really cares about Mike the door behind David is closed, but when Mike walks in that door is wide open, and it remains open until it's suddenly closed when Mike warns David that if he ever goes to Minsk he'd better watch out.
The One With Ross's Inappropriate Song - S9-E7
Continuity mistake: When Chandler turns around and Joey watches the football game, the door to Chandler and Monica's room is open. However, when Joey sees the sex part of the tape in the next shot, as Chandler is about to turn around and the TV screen is visible, the door is shut. (00:14:29)
The One With Ross's Inappropriate Song - S9-E7
Continuity mistake: When the veal is served, Phoebe looks at her plate twice. (00:16:55)
The One With Ross's Inappropriate Song - S9-E7
Continuity mistake: When Ross is holding Emma, the position he is holding her changes.
The One With Rachel's Other Sister - S9-E8
Continuity mistake: When Amy and Rachel are arguing in Monica and Chandler's apartment, the door behind Amy leading to the guest room changes from open to closed in almost every shot. (00:19:05)
The One With Rachel's Other Sister - S9-E8
Continuity mistake: When Rachel tells Amy that she'll let her use the Ralph Lauren discount Amy hugs her, and the glass Amy's holding in her left hand switches to her right hand and then back to her left hand, between shots.
The One With Rachel's Other Sister - S9-E8
Continuity mistake: When Ross, Rachel, and Amy arrive at Monica and Chandler's apartment the table is set, and there are folded napkins in napkin rings on the plates at each place setting, but after Amy insults Joey all the napkins have vanished.
The One With Rachel's Other Sister - S9-E8
Continuity mistake: When Chandler puts the box of china down on the chair, the lid of the box is shut, but a bit later the box is wide open.
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 With Rachel's Phone Number - S9-E9
Continuity mistake: Near the end when Rachel runs after Phoebe and Mike to ask Mike if the guy from the bar called, she leaves the apartment with her bag, which she places over her left shoulder. When she is talking to Mike the bag is gone, and then when she returns to the apartment she has her bag again. (00:20:30)
The One With Christmas in Tulsa - S9-E10
Continuity mistake: After Chandler says "Merry Christmas" to the gang, they all respond - Phoebe just goes "blargh blargh", and has her hands in her lap. They all turn to look at her, and suddenly her hands are resting on the sides of the stool. (00:10:30)
The One With Christmas in Tulsa - S9-E10
Continuity mistake: When the group notice that it's snowing outside, external shots show a lot more snow than the internal shots. (00:19:20)
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.