The One With The Rumor - S8-E9
Other mistake: Monica and Chandler's wedding is May 2001 (we are given the dates by the characters on the show, so it doesn't matter when the show aired.) And Rachel reveals at the wedding that she is pregnant, so that means she got pregnant in April or so of 2001. "The One With The Rumor" aired and is set to take place at Thanksgiving 2001, during which time Rachel should be 7 months pregnant. But her stomach's flat as a pancake. (00:01:15)
The One With The Rumor - S8-E9
Continuity mistake: After Will has arrived and Chandler says, "I'm watching the game but I'm not deaf," you can see Will in the background with his hands on his hips. When the camera switches to just Will and Monica, Will suddenly has two wine glasses in his hands. (00:06:20)
The One With The Rumor - S8-E9
Continuity mistake: In the episode with Brad Pitt in it, when Ross and Will are standing by the fridge and Rachel comes in, Will's right hand jumps around after he crushes the decoration on the wall. (00:08:40)
The One With The Rumor - S8-E9
Continuity mistake: When Rachel is offering Will the yams, the spoon that's in the dish is facing Rachel. When the shot changes to Joey lifting up the Turkey, the spoon is suddenly on the other side of the dish and facing towards Will. (00:11:05)
The One With The Rumor - S8-E9
Continuity mistake: When Will is demanding yams, it shows Ross looking towards the door; the camera then cuts to Will, and Ross is now looking at Will without time to move his head. (00:11:55)
The One With The Rumor - S8-E9
Continuity mistake: When Ross hands Rachel the Yams in order to break the tension, the amount of food on both Ross' and Will's plates changes between shots. Also several wine glasses appear on the table. (00:12:30)
The One With The Rumor - S8-E9
Continuity mistake: The gang confronts Ross over his affair with a fifty-year old librarian when he was younger. If you watch the mirror behind him (in one of the girls' rooms), it changes angles every time the camera cuts between Ross and the rest of the gang. (00:17:40)
The One With The Rumor - S8-E9
Continuity mistake: Right near the end of the episode when Joey comes in wearing the maternity pants, he pulls out the chair from the table twice. (00:21:20)
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.