The One With The Apothecary Table - S6-E11
Visible crew/equipment: When Rachel and Phoebe are talking in front of the Pottery Barn window, a wooden set wall covered in several signs is visible on the far right in the shots of Rachel.
The One With The Apothecary Table - S6-E11
Visible crew/equipment: Right after the "I'll Be There For You" intro, the camera shows the view from outside the "Central Perk" café. As it does so, a couple of stage lights are visible through the upper part of the window, obviously part of the set on the inside of the building.
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 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 With The Joke - S6-E12
Continuity mistake: In the coffee house scene when Joey reveals that he is working there, the strap on Joey's apron goes back and forth from being twisted around his neck and then straightened out. (00:10:50 - 00:12:50)
The One With The Joke - S6-E12
Continuity mistake: At the end Rachel turns away from Gunther and pulls her sleeves above her elbows. Next shot they are below her elbows. (00:20:00)
The One With The Joke - S6-E12
Visible crew/equipment: When Joey announces that Central Perk will be closed for an hour he shows everyone to the door, and in the wideshot of people walking out the door we can see the camera turning at the top right side of the screen, just before the shot cuts away.
The One With The Joke - S6-E12
Continuity mistake: In the scene in the coffee shop where Joey tells his friends about him closing down the coffee shop when he went to the audition, as Rachel says "He left work in the middle of the day to do a personal errand?" two men walk past behind the group. As she continues talking just a few moments later, the same exact men walk past again.
The One With Rachel's Sister - S6-E13
Visible crew/equipment: After Jill comes to Monica's apartment, they are all around the table in the living room. As the camera is moving from Jill, to Monica and Chandler, who are sitting on the couch, a camera-man is visible in the kitchen behind them, complete with camera and trailing wires. (00:04:15)
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 previous episode Monica had a very bad cold. This episode carries on immediately after the end of the last one (Monica's still in her dressing gown from earlier), but Monica isn't coughing or sneezing at all anymore. (00:00:05)
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 Where Chandler Can't Cry - S6-E14
Continuity mistake: When Chandler throws his copy of "Chicken Soup for the Soul" under the sofa and it goes across the floor to Monica's feet, she kneels down to pick it up by the counter next to the door, but when she rises, she's next to a chair that's under the table. (00:12:20)
The One Where Chandler Can't Cry - S6-E14
Continuity mistake: Jill goes to Ross' place, intending to make Rachel mad. When Ross goes to Rachel's to talk to her afterward, she rolls up her sleeves saying, "I'll give you something to think about." When Rachel is next shown, her sleeves are rolled down. Her arms also go from by her sides to crossed in front of her. (00:19:10)
The One Where Chandler Can't Cry - S6-E14
Visible crew/equipment: While Rachel's looking out Monica and Chandler's window she tells Joey that Ross is on a date with her sister, and just as Joey comments, "I didn't know we could date your sister," a crewmember can be seen moving around near the front door at the left side of the screen, and we know it's not Chandler or Monica since they're still in the bedroom wearing robes in the next shot.
The One Where Chandler Can't Cry - S6-E14
Continuity mistake: When they're watching the vampire video, Monica, Chandler, and Rachel are sitting on the couch, but in the closeups of the TV we can see the couch in the reflection and it's empty.
The One Where Chandler Can't Cry - S6-E14
Continuity mistake: In this episode Chandler says he can't cry, but in series 4 when he broke up with Kathy he was seen crying, and other times - it's just this episode it's apparently an issue.
The One Where Chandler Can't Cry - S6-E14
Continuity mistake: In the beginning of the episode when Joey tells Chandler that he hasn't forgiven him for kissing one of his sisters, Monica and Chandler's TV, entertainment set and ferns are missing from the set and there are cables protruding from the wall. The area is completely bare except for the French poster. Everything's back to normal slightly later in the episode.
The One That Could Have Been, part 1 - S6-E15
Revealing mistake: In the opening credits for both parts, fat Monica jumps on the couch and it lifts up on Chandler's end. If you look carefully at Chandler, you can see him holding one end of the couch with his hand and pressing up with his foot. (00:02:10)
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)
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.