The One With The Apothecary Table - S6-E11
Visible crew/equipment: After Ross and Rachel cover the table with the sheet, when Phoebe walks in Rachel says they can turn out the lights and watch the movie, and in the next shot we can see the end of the set wall, the soundstage and a crew member's leg.
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.