The One with the Stoned Guy - S1-E15
Continuity mistake: When the stoned guy says they should make macaroni and cheese, Monica holds out her hands. In the next shot, her hands are clasped together. (00:18:50)
The One with the Monkey - S1-E10
Continuity mistake: When Rachel says about her 6th date with Paulo, she is holding a decoration for the tree. In the next shot the decoration changes to a much larger object. Then, in the next shot, as she hands it to Monica, it has turned back to the original shape. (00:05:40)
The One with the Thumb - S1-E3
Continuity mistake: When Phoebe sees Lizzie, she is sat near her trolley feeding pigeons which are out of shot. In the next shot two pigeons have appeared next to the trolley. (00:11:40)
The One with Two Parts: Part 1 - S1-E16
Continuity mistake: Just after Marcel switches the TV to "SAP," Joey comes back and tells Chandler about Ursula and how she gave him extra food. Chandler is holding a bottle of water, and before the camera cuts to Joey it is open, but when he is talking it is capped, and finally when Chandler says "Score," the bottle is open again. (00:07:05)
The One with the East German Laundry Detergent - S1-E5
Continuity mistake: When Joey and Angela talk in Central Perk, the black waitress with long hair is visible the background of shots of Angela. When we see shots of Joey the same waitress is also behind him near Gunther. She is in two places at once. (00:05:50)
The One with the Thumb - S1-E3
Continuity mistake: When Monica is first explaining to her friend in the restaurant that her friends don't like anyone she dates, she is putting food onto a plate. The food changes between shots.
The One with the East German Laundry Detergent - S1-E5
Continuity mistake: When Rachel says 'everything looks like jammies now' she is holding up a t shirt. In the next shot as she throws it down, it is now folded up. (00:17:00)
The One with the East German Laundry Detergent - S1-E5
Continuity mistake: When Rachel is holding the ice pack to Ross's head at the end of the episode, Ross' left hand is lowered, then in the next shot, it is raised to his head. (00:21:35)
The One with the Thumb - S1-E3
Continuity mistake: When Lizzie holds the tin foil hat up to Phoebe, in one shot she holds it out with one hand, then in the next shot she is holding it in both hands. (00:12:10)
The One with the Sonogram at the End - S1-E2
Continuity mistake: When Rachel asks Phoebe if she is a twin, she is wiping the table next to her. In the next shot Rachel has her hands together. (00:11:40)
The One with the Dozen Lasagnas - S1-E12
Continuity mistake: During the scene where Phoebe is telling Rachel that Paolo made a pass at her, Rachel unrolls a long length of kitchen roll. During the scene there is a shot over her shoulder where we see that the kitchen roll is as normal and in the next shot we see it unrolled again. (00:15:30)
The One Where the Monkey Gets Away - S1-E19
Continuity mistake: After Ross asks Marcel to bring him the rice, he picks up his chopsticks. In the next shot, he is holding a napkin. (00:02:15)
The One with the Fake Monica - S1-E21
Continuity mistake: When the girls are at the dance club Rachel has a watch on, and it appears and disappears throughout the scene. (00:05:15 - 00:06:15)
The One with the Sonogram at the End - S1-E2
Continuity mistake: At the start of the episode when Chandler is talking about Pink Floyd, his legs are both on the table. When the shot changes, his right leg is resting on his left knee. (00:00:50)
The One with the Thumb - S1-E3
Continuity mistake: When Chandler says he won't quit smoking, he holds his hands out. In the next shot, they are lowered between his legs. (00:06:00)
The One with the Dozen Lasagnas - S1-E12
Continuity mistake: In The One Where Ross Finds Out he's having a boy (series 1), just before Rachel lets it slip, she is sitting on the edge of a chair eating a cookie. Watch her dress, it changes back and forth from being undone from the waist up, to only having two buttons open at the top. (00:19:55)
The One with the Stoned Guy - S1-E15
Continuity mistake: When Chandler says he can't work out what he wants to do working at his job, he is standing behind the sofa. In the next shot, he is in front of the sofa sitting down. (00:02:50)
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 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 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)
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.