The One After Joey And Rachel Kiss - S10-E1
Continuity mistake: At the end of this episode, Ross enters the door of Joey's apartment and finds Rachel and Joey kissing. Rachel says "I'm so sorry". The next episode, The One When Ross Is Fine, shows the same scene but it has been changed: Rachel never says "I'm so sorry". Joey starts talking when Ross enters the room.
The One With The Birth Mother - S10-E9
Audio problem: When Monica and Chandler are talking about telling Erica, when Monica says "Technicality!" It doesn't match with her lips. (00:15:30)
The One With Ross's Grant - S10-E6
Visible crew/equipment: When Dr.Hobart enters the meeting room to conduct the grant interviews, markers can be seen on the floor around the first chair's wheels as well as in front of the table. (00:12:25)
The One With Rachel's Going Away Party - S10-E16
Plot hole: In this episode Chandler finds furry black handcuffs, and everybody says that they have never seen them before. How is that possible considering all the people that have moved in and out of that room? How come nobody noticed them when the room and closet were painted green after being pink?
The One With The Home Study - S10-E7
Other mistake: In the opening scene Chandler smiles at Ross' joke while playing with the ball in his hands. Later on in the scene Ross cracks another joke and the exact same scene of Chandler smiling and fiddling with the ball is repeated. (00:00:40 - 00:01:10)
The One With Rachel's Going Away Party - S10-E16
Revealing mistake: The twins are dolls. They don't move, and the way they are being carried indicates they don't weigh much.
The One With The Home Study - S10-E7
Continuity mistake: When Chandler kisses Monica before letting the social worker in, she puts her hand on his arm. The camera cuts to her and she says "Tongue, really?" but her hand is by her side now. The camera cuts back to Chandler and both her hands are now out in front of her.
The One Where Estelle Dies - S10-E15
Continuity mistake: Just after the opening titles cut to Central Perk, four people can be seen having a conversation through the window. In the next shot, there is one person sitting next to the window and a waitress has appeared out of nowhere. (00:03:05)
The One Where The Stripper Cries - S10-E11
Revealing mistake: When Monica collapses onto the beanbag chair at the very end of the episode, we can see the bottom of her fat suit below the hem of her skirt.
Other mistake: When Rachel attempts to board the plane the first time, the man at the desk looks at her passport upside down.
The One Where The Stripper Cries - S10-E11
Visible crew/equipment: In the scene with the conversation with the stripper, there is a large vase on the kitchen table. Several lights, the top of the stage and a few crew members are reflected in it.
Continuity mistake: When Ross is talking to Phoebe and Joey in Central Perk, a strand of Phoebe's hair keeps getting snagged behind the buttons of her blouse and hanging loose again with her other hair several times during the scene. (00:12:40)
The One Where Joey Speaks French - S10-E13
Other mistake: When Joey auditions near the end and Phoebe steps in to explain to the producer/audition guy, she speaks French and the subtitles say, 'He is a little bit retarted' instead of 'He is a little bit retarded.' (00:18:35)
The One With Princess Consuela - S10-E14
Visible crew/equipment: When Ross enters Central Perk with champagne, straight away when he walks over to the sofa, look above the door. In the reflection of the top window, you can see several stage lights. (00:08:45)
The One After Joey And Rachel Kiss - S10-E1
Continuity mistake: Chandler, Monica and Phoebe are shown listening at the wall between their room and the room Ross is in with Charlie. However, when Ross comes into the room, the outside hallway is shown, and it is clear that the wall they were listening at actually connects to the hallway, not another room. Ross even walks in that direction when he leaves, proving it's not a dead end or similar. (00:05:30)
The One With Princess Consuela - S10-E14
Continuity mistake: When Phoebe and Mike are at Central Perk discussing their name changes, his scarf goes from being hung loose around his neck to tied around his neck from shot to shot. (00:12:15)
The One With The Cake - S10-E4
Continuity mistake: Just before Rachel and Ross come back from the cake store, Monica is holding Emma on her lap. Emma is holding a green toy in one shot, when the camera angle changes it is nowhere to be seen. (00:19:30)
Continuity mistake: In the hospital when Erica is giving birth and the camera is on the doctor, the door to the room is closed. However, when the camera angle changes, the door is wide open even though no one had entered or exited.
The One With The Cake - S10-E4
Continuity mistake: At the end after Rachel and Ross have come back from the cake store, when they are asking Emma how old she is, we can see Joey walking to sit down, then in the next shot he is sat down, then walking to sit down again. (00:20:25)
The One After Joey And Rachel Kiss - S10-E1
Factual error: There is an impossibility with the hotel rooms in Barbados. Ross gets from Monica and Chandler's room to Rachel's room far too quickly for it to be real. Also, when the camera moves between rooms (cutting through the wall), you can see that both Rachel and Ross' rooms are too long. If the walls were where they actually are, they would edge through into Monica and Chandler's room. (00:05:05)
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.