The One With Joey's Porsche - S6-E5
Visible crew/equipment: In the scene where Phoebe knocks over the vase, after she says, "Well, that's just the way things go" and turns around to face the babies again, you can see a crew member coming out of Rachel's room. When Phoebe starts looking for the missing baby, the shadow of the crew member is visible on the right of the screen as the baby is placed in the drawer. (00:15:30)
The One With Joey's Big Break - S5-E22
Audio problem: At the very end when Ross hits Rachel's stomach twice the sound doesn't match his actions. (00:21:00)
The One With The Rumor - S8-E9
Continuity mistake: After Will has arrived and Chandler says, "I'm watching the game but I'm not deaf," you can see Will in the background with his hands on his hips. When the camera switches to just Will and Monica, Will suddenly has two wine glasses in his hands. (00:06:20)
The One With The Stripper - S8-E8
Continuity mistake: At the end of this episode, before the credits, Monica is giving a striptease for Chandler. Notice how the crown on his head changes position. Look at the coloured circles on this crown. (00:19:10)
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 with Two Parts: Part 1 - S1-E16
Continuity mistake: When Chandler is playing with the toy in his office, his right hand moves between shots. (00:09:35)
The One Where Rosita Dies - S7-E13
Continuity mistake: In this episode we seemingly understand why Ross and Monica's parents favor Ross. In one scene at Monica's apartment Ross says that it is because their parents thought Judy was barren. This would make sense except that in TOW Rachel's Book, Jack and Judy tell Monica and Chandler that they had to get married because Judy was pregnant. Judy was using a diaphragm as birth control and Jack's dog ate it. It doesn't make sense that Judy would use a diaphragm if she thought she was barren. This was not news to Monica since she said she had heard the story about the dog eating her mother's diaphragm at her 5th grade Halloween party. (00:04:15)
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 With The Flashback - S3-E6
Continuity mistake: Phoebe and Ross are in the soon to be closed bar sitting on the pool table. He clears it of everything, but a few seconds later he stops making out because the "damn balls are in the way" and somehow magics up a handful of snooker balls. If you look closely when he's clearing the table, there are two dark balls at the side which he studiously ignores, and which Lisa Kudrow then surreptitiously grabs and takes onto the table with her so David Schwimmer can grab them later. (00:19:35)
The One With The Lottery - S9-E18
Continuity mistake: In the scene where Joey and Phoebe are holding the lucky bone, which they have to break and make a wish, look at Joey's thumb; the location of it changes between shots. (00:05:40)
The One With All The Kissing - S5-E2
Continuity mistake: When Phoebe says she is going to "pack her ass off" she walks toward the coffee house door, and they cut to a quick shot of Joey then back to the wide shot with the door, and Phoebe has disappeared. She did not have time to make it to the door and out. (Widescreen version). (00:15:50)
The One With The Jellyfish - S4-E1
Continuity mistake: Phoebe and her mother are in her mother's house at the beach. Phoebe has just found out that Phoebe senior is her real mother. Have a look at Phoebe's mother in this episode and the last episode of series 3 (The One At The Beach). Her hair is a lot shorter in series 4 even though no time has passed in the storyline. (00:03:35)
Continuity mistake: When Monica tells Joey and Ross she is not pregnant, her hand goes to her chest, then down to her side, and then back to her chest. (00:02:10)
The One With All The Cheesecakes - S7-E11
Continuity mistake: Chandler walks into his apartment to find Rachel eating cheesecake without him. As the door is shutting, the pen on the Magnadoodle is hanging loose; it can be heard hitting the door when Chandler is closing it. The next shot shows Rachel stop eating, and when we next see Chandler, the door is closed and the pen is in its holder. (00:15:50)
The One With the Breast Milk - S2-E2
Continuity mistake: At the start of the episode when we first see Carol breastfeed Ben, Susan puts a pillow under Ben's head twice. (00:00:30)
The One With All The Thanksgivings - S5-E8
Revealing mistake: When Joey has the turkey on his head, and Chandler is by the door, look at the wall to Chandler's right. It's a "wild wall" - i.e., a movable wall put there to extend the set outward an additional few feet, since the camera normally doesn't see that far forward. The wall angles oddly away from the room, and you can see how the line and pattern of the hallway floor continues into the room. (00:06:15)
The One In Vegas, Part 2 - S5-E24
Factual error: When Monica rolls an 8 to buy everyone a steak dinner, the one die is positioned with a 5 and 4 facing the camera (the 5 on the left, and 4 on the right). With the die that way round a 1 is always on top. There is no other way to get the 5 and 4 combo. This means that Monica had a 7 on the other die, That is impossible. And so she did not roll an 8. (00:31:35)
The One With The Embryos - S4-E12
Visible crew/equipment: When Rachel crosses the boys' apartment to see what is in the drawer, if you look up to the right, you can see a glimpse of a boom mic. (00:20:25)
The One With Rachel's Assistant - S7-E4
Continuity mistake: In the scene when Joey is talking to the producers of Mac and Cheese, he says, "We're not even shooting them anymore?!" As he says this he lifts his left arm up, but in the very next shot his left arm is back down by his side. (00:14:40)
The One With The Bullies - S2-E21
Revealing mistake: In the scene where Ross, Chandler, and the bullies are fighting in the street, an extra bumps the fire hydrant and it wobbles and slides over. (00:21:55)
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.