The One Where Chandler Doesn't Like Dogs - S7-E8
Revealing mistake: When Rachel and Tag are in the hall at the end of the episode, the tan mark from Jennifer Aniston's wedding ring is visible on her hand. (00:19:15)
The One Where Chandler Doesn't Like Dogs - S7-E8
Revealing mistake: While Monica is sneaking the dog back to her apartment and Chandler is in the toilet, as Monica lifts her hand to her mouth she whispers, "Up!" to get the dog to stick its head out of the handbag. (00:15:00)
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.