The One Where Rachel Tells... - S8-E3
Visible crew/equipment: When Phoebe asks Treeger not to mention the incident with the door to Monica and Chandler, just as Treeger uses the measuring tape we can see the opening in the wall beside the door.
The One Where Rachel Tells... - S8-E3
Visible crew/equipment: When Monica is yelling at the other couple on their honeymoon, the things on the shelves behind them shows the reflections of set lights. (00:15:25)
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.