The One With Ross' Step Forward - S8-E11
Continuity mistake: When Phoebe is getting drinks out of the refrigerator, she gets out two different type bottles, and they switch hands during the scene. (00:17:50)
The One With Ross' Step Forward - S8-E11
Continuity mistake: It's obviously December, with the set decorations and Rachel's reference to sitting on multiple Santas' laps because she is randy from her pregnancy hormones. The characters establish that it's Rachel's fourth month of pregnancy...but she became pregnant about six weeks before Monica and Chandler's May 15 wedding. Her fourth month would have been in July, not December.
The One With Ross' Step Forward - S8-E11
Continuity mistake: In the scene when Phoebe comes in to tell Rachel she is sorry about the whole thing with Roger, Rachel is eating ice cream, and sets it on the counter and in the next shot sets it down again. (00:23:25)
The One With Ross' Step Forward - S8-E11
Other mistake: In the opening scene when Rachel says "I went from store to store sitting on Santa laps" the camera is out of focus.
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.