The One The Morning After - S3-E16
Continuity mistake: Right before Ross and Rachel storm in, the girls show Joey how much their waxing stuff hurts. Phoebe starts putting the wax on Joey's inner arm, but then the shot changes and she is spreading in on the outer side. Also she slaps the strip on and the blue tab is hanging down off his arm, but then the shot changes again and it is on his arm with the other end of the strip hanging off the other side. (00:11:10)
The One The Morning After - S3-E16
Continuity mistake: In previous episodes we've seen that from the living room there's a short wall just inside Monica's bedroom (presumably to prevent a clear view inside, as her bedroom set isn't normally there). However in this episode when most of the gang are in her room, they're listening right by the door into the living room with nothing in the way. (00:11:25)
The One The Morning After - S3-E16
Continuity mistake: When Phoebe, Chandler, Monica, and Joey are eating the organic wax, Monica has her feet up on the wall with her legs crossed left over right, but in Joey's closeups when he asks about needing a new walk, Monica's legs are crossed right over left. (00:18:00)
The One The Morning After - S3-E16
Continuity mistake: When Ross is listening to the message from Rachel there is not a wadded piece of paper on the counter, but after he sets the cup down the paper appears. (00:03:05)
The One The Morning After - S3-E16
Continuity mistake: When Monica and Phoebe get excited about being a "Waxine girl", Monica puts the mop upright against the counter and the mop falls over, but in Phoebe's closeup we see the mop is still upright behind her. (00:06:20)
The One The Morning After - S3-E16
Continuity mistake: While Rachel and Ross are fighting, when Rachel realises that she was at Ross' apartment at the same time as his "little friend", Ross holds out the newspaper (so she can hit him) with his left hand, but in the next shot it's held out in his right hand. (00:13:40)
The One The Morning After - S3-E16
Continuity mistake: When Ross is listening to the message from Rachel he takes a drink from a cup and sets it down, with the handle pointing toward the answer machine. In the next shot, a close-up, the handle is now towards the camera. (00:03:05)
The One The Morning After - S3-E16
Continuity mistake: When Ross is listening to Rachel's message on his answering machine, only the open pill bottle sits on the counter beside his mug, but then the bottle cap and cotton filler suddenly appear next to it. (00:03:00)
The One The Morning After - S3-E16
Continuity mistake: While Monica's preparing her shake in the blender she asks Rachel about the anniversary dinner, and when Rachel tells her that she and Ross broke up, Monica throws the blender lid and it flies over the counter, but in the next shot the lid is back in Monica's hand, and then it vanishes again. (00:01:10)
The One The Morning After - S3-E16
Continuity mistake: When Rachel asks, "When did Chloe leave?" the paper Ross is holding changes direction. Note the title of the paper: The New Yorker. (00:13:30)
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.