The One With The Secret Closet - S8-E14
Continuity mistake: In the scene where Rachel comes in to have Joey feel her stomach, he gets up from the bed and you can see the boxer shorts he is wearing. You can also see them at the end of the scene, even though he is supposed to be naked. (00:03:00)
The One With The Secret Closet - S8-E14
Continuity mistake: When Chandler mentions how long Alexandra has been massaging Monica, he is holding a bowl,and he walks away with it. But when Monica says to Phoebe, "you can understand why this would be weird for me", the bowl is on the table. (00:05:20 - 00:06:00)
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.