Continuity mistake: In the beginning in the coffee house, Ross is explaining to Phoebe and Rachel what 'Unagi' is. The blonde lady behind Phoebe is wearing light blue jeans. She then puts a brown leather jacket on, however in the next shot it has gone, only to reappear and disappear again. (00:03:20)
The One With Joey's Fridge - S6-E19
Continuity mistake: When Joey pushes Ross against the fridge, a box falls from the top of the fridge onto the shelf beside it. A few seconds later when Joey turns to Chandler, we can see over his shoulder that the box is back on the fridge. (00:08:55)
The One With Joey's Fridge - S6-E19
Continuity mistake: The handle to the fridge door is on the left, so when it opens the inside is visible. In earlier episodes the handle was on the right and it opened out towards the room, blocking the inside from view. (00:00:05)
The One With The Apothecary Table - S6-E11
Continuity mistake: The red eraser knob on the magnadoodle changes from one side to the other, when Janine is going out to tell Monica she is sorry. (00:18:00)
The One Where Ross Got High - S6-E9
Continuity mistake: When Ross finishes the trifile, a small amount of whipped cream appears and disappears throughout a few shots. (00:16:35)
The One With The Ring - S6-E23
Continuity mistake: When Rachel is talking to Monica about Paul crying, just before Rachel leaves, Monica has her hair over her left shoulder; the shot cuts and she now has most of her hair over her right shoulder. (00:09:50)
The One Where Paul's The Man - S6-E22
Continuity mistake: When Monica is listening to the answering machine, the bread in the blue and white bag behind her changes position. (00:12:40)
The One With Ross's Denial - S6-E3
Continuity mistake: When Joey is interviewing the potential roommate and Chandler comes in, Joey's stance changes a few times. His grip on the application form changes, and when he points to the bathroom his arm is in a slightly, but noticeably, different place in the next shot. (00:11:10)
The One With Joey's Porsche - S6-E5
Continuity mistake: When Ross is talking to his divorce lawyer there are 2 pens in a holder on the desk. Throughout the scene they vanish and appear randomly. (00:10:50)
The One With The Ring - S6-E23
Continuity mistake: Paul finally opens up, and cries like a baby to Rachel. While talking to her at the breakfast bar in the kitchen (when Rachel is trying to distract him with sex), he's wearing a white linen shirt that constantly changes between tear-stained and wrinkled to ironed and clean. (00:14:35)
The One Where Paul's The Man - S6-E22
Continuity mistake: When we hear the recording of Chandler answering the phone, it sounds nothing like what Chandler actually said. (00:13:00)
The One With The Joke - S6-E12
Continuity mistake: Joey and Chandler are talking about money, and Joey picks up the Playboy magazine saying Ross gave him reading material. He sets it down on the counter, but in the next shot of the magazine, it has moved farther down the counter. (00:03:10)
The One With Rachel's Sister - S6-E13
Continuity mistake: When Jill drops her shopping bags on the coffee shop table, the small blue Tiffany's bag is visible on the end of the 'line'. But it is not visible in any shots after Rachel comes in. Additionally, when Rachel grabs the bags and leaves, Ross seems to pick the little blue bag up off the floor, though it is not shown how the bag got there. (00:05:35)
The One Where Chandler Can't Cry - S6-E14
Continuity mistake: In the cafe, Ross says to Rachel, "I'll tell her we can't see each other any more," and we see Rachel bring her hands down from her face. However, in the previous shot we had already seen her lower her hands. (00:03:25)
The One On The Last Night - S6-E6
Continuity mistake: At the end when Monica and Chandler hug, Monica's arms keep going from under to over Chandler's arms as the cameras switch many times. (00:20:00)
The One That Could Have Been, part 1 - S6-E15
Continuity mistake: Near the start, Chandler is sitting in the coffee house in the big chair. When he's talking to Joey about money, his feet change positions every two seconds. On the floor, crossed, resting on the table, the list goes on and on. (00:04:55)
The One Where Paul's The Man - S6-E22
Continuity mistake: When Monica is blaming Phoebe for Chandler hearing the wedding message, Phoebe puts the magazine down on her lap and it's closed, but in the next shot it's open. (00:15:40)
The One With The Joke - S6-E12
Continuity mistake: In the coffee shop Phoebe is not in the scene. After Joey puts his apron on, the camera shows Phoebe is next to Rachel. Monica asks Joey if he works there, he says no, a customer calls "waiter" and in a full view of the coffee shop Phoebe is no longer there. (00:09:45 - 00:10:55)
The One Where Ross Got High - S6-E9
Continuity mistake: When Ross asks Rachel to step into the hallway, we see the whipped cream atop the trifle dessert plates on the table, but while Joey gives everyone acting lessons all the whipped cream is gone, then the dollops of whipped cream reappear once again.
The One With The Proposal, part 1 - S6-E24
Continuity mistake: When the waitress opens the door to the kitchen to tell Monica about a complimentary customer, in the first shot the waitress pulls the door open and stands in front of it, but in the next shot she's pushing the swing door into the kitchen poking her head in to talk to Monica. (00:20:35)
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.