The One With The Home Study - S10-E7
Continuity mistake: When Ross and Rachel are pushing Emma on the swing, the legs of Emma's pants change position several times between shots. At first they are pulled up with her legs exposed, then they are down further, and in the last shot when Ross gets kicked, they are pulled up again.
The One After Joey And Rachel Kiss - S10-E1
Visible crew/equipment: After Monica whips her hair around and smacks herself in the face with all the shells in her hair, it cuts to Ross at his apartment, and the end of the set wall can be seen at the right side of the screen, with the sound stage visible. (00:21:45)
The One Where The Stripper Cries - S10-E11
Visible crew/equipment: At the end, when Ross and Chandler are arguing about what bed Rachel was on (in the flashback), a line of stage lights is visible in the copper pans behind them. (00:21:40)
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 Rachel's Going Away Party - S10-E16
Continuity mistake: The level of beer in Ross' bottle goes up and down between shots as he's talking to Joey at the kitchen table. (00:12:00)
The One With The Cake - S10-E4
Visible crew/equipment: When Monica is talking to Chandler about waking Emma up, as she walks over to him, crew lights are visible in the top left corner of the screen. (00:05:35)
The One With The Cake - S10-E4
Revealing mistake: When Rachel and Ross are on the way back, if you look at Ross you can see a purple tinge to the side of his face. This is from projecting the background. (00:17:30)
The One Where Joey Speaks French - S10-E13
Other mistake: When Chandler, Monica and Erika arrive back at the apartment after sightseeing, Chandler enters the apartment from the left (past where their apartment door is) rather than from the right, as if he came up the stairs. He obviously is entering from the stage and didn't take the time or cue to appear to enter from the direction of the stairs.
The One Where Estelle Dies - S10-E15
Revealing mistake: When Chandler and Monica are at the door of the house you can see that it is a fake background behind Chandler. (00:09:35)
The One Where Estelle Dies - S10-E15
Continuity mistake: The second time Ross visits Mr. Zelner, he hands him a pterodactyl egg replica. The hole in the egg switches between the top or bottom, depending on the shot. (00:14:40)
The One Where Estelle Dies - S10-E15
Continuity mistake: When Rachel walks in with Emma, Ross is on the laptop. It is straight and on the table, in a later shot,the laptop has moved and is over the edge of the table. (00:18:50 - 00:20:55)
The One After Joey And Rachel Kiss - S10-E1
Visible crew/equipment: When Monica is waving around her shellfish hairdo in the final scene at the hotel, the camera zooms out. When it does this, look at the top of the set. Not only can you see where the set ends, but you can also see the stagelights, hanging equipment etc. (00:12:10)
The One With Ross's Grant - S10-E6
Continuity mistake: When Aisha Tyler and Greg Kinnear put one hand on Ross's face, they bring those hands together and they interlock fingers, then the camera changes positions and they interlock fingers again. (00:22:20)
Continuity mistake: When Monica and Chandler walk into the apartment with the twins, 2 very bright yellow soothers keep appearing and disappearing from the babies' mouths. (00:18:50)
The One With Princess Consuela - S10-E14
Continuity mistake: When Ross is trying to get Rachel's chair through the revolving doors, he has his right leg on the chair but it suddenly switches to him having his left leg on the chair. (00:15:25)
The One With The Cake - S10-E4
Plot hole: Judy says that both her parents died very young. However, we saw her mother's death in "The One Where Nana Dies Twice" and she was quite old. Also, in Season 7, 'TOW Phoebe's cookies', Jack Geller tells Chandler that his father in law still thinks he is a lawyer and says "So if you ever see me giving them legal advice, just nod along," implying that Judy's parents were both still alive.
The One Where Joey Speaks French - S10-E13
Visible crew/equipment: When Joey is calling Phoebe after she walked out of his apartment, the shadow of a camera can be seen on Monica's door. (00:08:05)
The One Where Chandler Gets Caught - S10-E10
Continuity mistake: Ross claims he looks into Monica and Chandler's and watches them eating dinner and watching TV. His apartment is a floor lower down than theirs and with the balcony wall, the sofa and tables distance from the window and the fact the bottom of the window is higher than the floor, there is no way Ross would be able to see that far in. We have seen in the past that he can basically only see who is at the window. (00:19:05)
The One Where Ross Is Fine - S10-E2
Audio problem: When Ross is drunk and talking to Rachel, Joey and Charlie on the couch in his apartment; he begins to say "Where do you think we can go?" but his mouth does not move. (00:12:10)
The One With The Cake - S10-E4
Visible crew/equipment: After Rachel announces that Phoebe and Joey will perform something, Phoebe asks Joey if he'll be nervous because he has nothing prepared, and when Joey replies that he does it every day with three cameras pointed at him, it's perfect timing that in the next shot we can see filming equipment at the right side of the screen.
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.