The One With The Donor - S9-E22
Visible crew/equipment: After Chandler explains to Monica why he brought Zack home, just as Chandler leans over the couch to hand Zack the bottle of beer, the camera and a crew member can be seen at the left side of the screen.
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.