The One Where Chandler Can't Remember Which Sister - S3-E11
Continuity mistake: Ross is on about going to Maryangela's to Chandler. He picks his drink up, the camera cuts and he picks it up again. (00:12:45)
The One Where Chandler Can't Remember Which Sister - S3-E11
Continuity mistake: When Joey is saying about ticking his Grandma off, he has his hands up in front of him. When the shot changes, his hands are lowered. (00:13:20)
The One Where Chandler Can't Remember Which Sister - S3-E11
Visible crew/equipment: When Phoebe and everyone else hear the guy upstairs with the "pogo stick" Joey gets up to give him the "butt kicking of a lifetime," and just as Joey walks around the couch we can see a crew member and camera, at the left side of the screen.
The One Where Chandler Can't Remember Which Sister - S3-E11
Continuity mistake: When Rachel gets off the phone with Mark she sets the phone on the counter. In the next shot the phone is in the holder and it keeps going in and out.
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.