The One Without The Ski Trip - S3-E17
Continuity mistake: When Monica and Phoebe enter the coffee house and talk to Chandler and Ross, the extra sitting at the coffee bar (black shirt, blue jeans) is not wearing a belt, then when they pan again she is, and back she is not. (00:00:12 - 00:00:54)
The One Without The Ski Trip - S3-E17
Continuity mistake: At the start, just as Rachel is leaving Joey's apartment after mentioning the tickets she's got, Joey stops her and she turns round. Her hands are clasped together in front of her chest in one shot and by her side in the next. (00:04:00)
The One Without The Ski Trip - S3-E17
Continuity mistake: When Chandler tells Rachel to "shut up; you're not my mom," Joey has both hands on the bottom of the Chinese food carton. In the next shot his right hand is on top of the box. (00:05:30)
The One Without The Ski Trip - S3-E17
Continuity mistake: When Phoebe is saying how she gets out of tickets, she is pointing at herself in one shot and not in the very next shot. (00:05:50)
The One Without The Ski Trip - S3-E17
Continuity mistake: Just before Ross leaves the rest stop, Phoebe goes over to him and says,"Maybe we can see a movie or something. Or the rodeo." When she says this, she takes a step back from Ross twice. (00:20:20)
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.