The One Where Phoebe Hates PBS - S5-E4
Continuity mistake: In the opening scene where Rachel is checking the mail and is walking over to Monica's room, she has a pair of pumps on, then once she has walked in on Monica and Monica runs after her to say she was taking a nap, Rachel is wearing a pair of backless high-heeled sandals, then when Joey and Ross come in, Rachel is wearing the pumps again (we see this when Ross says "I had to talk loud because the movie was loud"). (00:00:10)
The One Where Phoebe Hates PBS - S5-E4
Continuity mistake: Monica comes to get her pan back from Chandler, and when she opens the door, the magna doodle pen is hanging down. The shot changes and it is attached to the board; it changes again and it is hanging once more. (00:12:00)
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.