Trivia: A bit too unlikely to be just a coincidence, but I can't work out the significance. The doctor who delivers Phoebe's triplets (the one who loves Fonzie) played the evil head of Wolfram and Hart in "Angel". The doctor who delivers Erica's twins in this episode also plays the evil head of Wolfram and Hart in "Angel" (after the death of the first guy).
Trivia: In the scene where Monica and Chandler hold their twins for the first time, a nurse can be heard paging "Dr. Matthew Perry" and "Dr. Green" on the intercom.
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.