The One with the Stoned Guy - S1-E15
Continuity mistake: Just before Chandler tells everyone he quit, he holds out both hands in front of him. In the next shot, his left hand is by his side. (00:02:05)
The One With The Video Tape - S8-E4
Continuity mistake: When Chandler says about Ross and Rachel having a baby, He lifts his bottle to have a drink, camera changes and he raises it again. (00:02:25)
The One With Monica and Chandler's Wedding, Part 2 - S7-E24
Continuity mistake: As Chandler meets Monica at the altar, Monica's hand switches from holding Chandler's hand, to holding the flowers, with no time to do so. (00:40:40)
The One with the Stoned Guy - S1-E15
Continuity mistake: In the scene where Monica is explaining to Rachel that she has hired her friend Wendy as her waitress, Rachel is holding a water bottle in one hand and the cap in the other. Monica moves towards her and Rachel is pointing her hand in Monica's direction and then in the next shot we see Rachel from another angle and her hand is holding the cap on top of the bottle too fast to have happened in normal time. (00:08:40)
The One With the Male Nanny - S9-E6
Continuity mistake: In The One With the Male Nanny in series nine, near the end of the episode Ross gets a beer when he is argung with Rachel as to whether they should fire him. During shots, the label on the bottle moves round. (00:25:05)
The One With Ross' New Girlfriend - S2-E1
Continuity mistake: At the very beginning of the episode, the blood on Rachel's head changes a few times throughout that opening scene. (00:01:15)
The One With Ross's Denial - S6-E3
Continuity mistake: When Joey is interviewing the potential roommate and Chandler comes in, Joey's stance changes a few times. His grip on the application form changes, and when he points to the bathroom his arm is in a slightly, but noticeably, different place in the next shot. (00:11:10)
The One In Barbados, part 2 - S9-E24
Continuity mistake: When Monica and Mike play table tennis and Monica says "I think that may have missed the table" there is no one sitting in the chairs behind her. The shot then cuts to Mike and he replies "oh do you?" The shot then cuts back to Monica, she replies "er, yeah" and there are suddenly two people sitting in the chairs behind her. Then in the next shot of Chandler and Phoebe the women who were just in the chairs are now walking behind Chandler and Phoebe in the direction of the chairs, and in the next shot they take their seats. (00:38:40)
Continuity mistake: When the friends put down their keys, the keys' positions change when the camera pans the apartment. (00:25:30)
The One With the Holiday Armadillo - S7-E10
Continuity mistake: In the scene where Ross takes a liquorice from the skull, in the first close up shot he is holding it in his hand, but then immediately after this when they zoom out, he is chewing a piece. This is impossible because he would have had no time to bite it. (00:00:50)
The One After the Superbowl, part 1 - S2-E12
Continuity mistake: When 'Drake' is having dinner with Erica (the stalker), Joey is seen to be wearing a ring on the ring finger of his left hand. This can been seen just before another diner begins to choke. When the episode cuts back to them in the restaurant, the ring is gone. (00:09:50)
The One Where the Monkey Gets Away - S1-E19
Continuity mistake: When Ross and Rachel argue about losing Marcel, the bottle of wine Ross re-corks is sitting on the table. Neither of them touch the bottle at any point after this yet when the woman from animal control arrives, the bottle has moved to the side table. (00:10:15 - 00:11:10)
The One With Monica and Chandler's Wedding, Part 2 - S7-E24
Continuity mistake: The way Phoebe holds her flowers when told to smile changes depending on the angle. (00:04:30)
The One with George Stephanopoulos - S1-E4
Continuity mistake: When Joey jumps over the sofa to give Ross the tickets, one of the pages of Ross's magazine is sticking out towards him. In the next shot it is gone. (00:02:40)
The One With Joey's Porsche - S6-E5
Continuity mistake: When Ross is talking to his divorce lawyer there are 2 pens in a holder on the desk. Throughout the scene they vanish and appear randomly. (00:10:50)
Continuity mistake: Near the end when Monica and Chandler are going on to dance for the last time, Monica speaks and her hair is neatly behind her right ear. The shot then looks to Chandler before going back to Monica immediately. However her hair is suddenly behind her left ear when she can't have moved it as her hands are in the shot at all times. (00:21:15)
The One Where the Monkey Gets Away - S1-E19
Continuity mistake: When Phoebe gets hit with the tranquilizer she falls on the couch with no dart in her leg. When she stands up it appears out of nowhere. (00:15:50)
The One With Chandler's Dad - S7-E22
Continuity mistake: When Monica and Chandler are in Las Vegas watching the burlesque show, Chandler turns the light on the middle of the table off to "hide" from his Dad. When Monica calls out saying "Waiter. Waitress.", the light is suddenly back on and remains on for the rest of the scene. (00:15:50)
The One With Rachel's Date - S8-E5
Continuity mistake: When Ross says goodbye to Rachel near the end, she lowers the bag of sweets to her waist. Then in a close up of her looking thoughtful it's up by her chest. (00:20:10)
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)
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.