The One In Barbados, part 1 - S9-E23
Trivia: When Joey and Rachel are looking for nametags to con their way into the convention, the name picked out for Rachel is Kate Miller. I just found it a bit odd that not a flicker of recognition passes across Joey's face, considering that was the name of Dina Meyer's character from a few seasons back who he was in love with.
The One With Ross's Inappropriate Song - S9-E7
Trivia: The joke in this episode, broadcast in 2002, about Richard having a tape of him having sex with Monica, Chandler watching the tape, and then Monica coming in and being furious that he hadn't noticed it wasn't her, plus getting annoyed about being taped over by Richard, is IDENTICAL to one in an episode of Coupling (UK version), broadcast in 2000.
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.