Visible crew/equipment: When Ross notices that Ugly Naked Guy is back, in the next exterior shot we can see the top of the set as everyone gathers at the window.
Visible crew/equipment: While everyone's in the apartment Ross is on the balcony talking to Emily on the phone, and in the mirror we can see the reflections of Phoebe and someone else wearing a blue shirt (with a large white pattern) and blue pants (looks like jeans), but none of the others are actually dressed like that.
Visible crew/equipment: Just as Monica and Rachel walk into the storage room, at the start of the shot the camera casts a shadow on the head sculpture which moves as the camera moves.
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.