The One Where Chandler Doesn't Like Dogs - S7-E8
Deliberate mistake: When Phoebe is trying to sneak the dog out of the apartment, the guys say that they have noticed that the bag is moving, yet the bag doesn't move at all. (00:04:10)
The One Where Chandler Doesn't Like Dogs - S7-E8
Deliberate mistake: Monica sees the dog on her settee from Ross's apartment, which wouldn't be possible from the angle as Ross's place is lower than Monica's. (00:04:50)
The One Where Chandler Doesn't Like Dogs - S7-E8
Factual error: When Monica and Chandler come back from Ross' apartment, Chandler opens the door and Monica appears from stage left when the stairs are stage right. (00:06:00)
The One Where Chandler Doesn't Like Dogs - S7-E8
Revealing mistake: While Monica is sneaking the dog back to her apartment and Chandler is in the toilet, as Monica lifts her hand to her mouth she whispers, "Up!" to get the dog to stick its head out of the handbag. (00:15:00)
The One Where Chandler Doesn't Like Dogs - S7-E8
Visible crew/equipment: When Chandler sees the empty dog basket on the floor at Ross' there is a panning shot to the door. If you look carefully, you can see a crewmember wearing blue jeans and white shoes. (00:17:25)
The One Where Chandler Doesn't Like Dogs - S7-E8
Revealing mistake: When Rachel and Tag are in the hall at the end of the episode, the tan mark from Jennifer Aniston's wedding ring is visible on her hand. (00:19:15)
The One Where Chandler Doesn't Like Dogs - S7-E8
Continuity mistake: In this episode, it is stated that Ross does not like ice cream because it's too cold. However, back in The One Where Ross Dates a Student, you can see Ross on a date with Elizabeth eating an ice cream.
The One Where Chandler Doesn't Like Dogs - S7-E8
Continuity mistake: When Rachel and Tag are on the balcony and Tag says, "What did Joey say? I like you back?" he is standing on the balcony with one hand in his pocket and the other in front of him. As the camera angle changes, Tag is now in a different position, with both his hands behind him, leaning against the balcony before he moves forward.
The One Where Chandler Doesn't Like Dogs - S7-E8
Continuity mistake: When Chandler is looking over Ross' list (right before he calls him Magellan), he has the front sheet of the paper folded up. In the next shot, the sheet is folded down.
The One With All The Candy - S7-E9
Revealing mistake: At the start of the episode, when Ross says, "No, one daddy, two mommies," Ben is mouthing the line along with him. (00:00:15)
The One With All The Candy - S7-E9
Continuity mistake: When Phoebe tries to show the gang she can ride her bike, the large metal bike rack at the curb changes position between shots. (00:09:50)
The One With All The Candy - S7-E9
Continuity mistake: When Phoebe sits on the swing (when learning to ride her bike), her scarf has one end down her front and the other over her left shoulder. In the next shot, the end is over her right shoulder instead of her left. A couple of shots later, it is switched back again. (00:11:05)
The One With All The Candy - S7-E9
Continuity mistake: When Ross is trying to convince Phoebe to try to learn to ride her bike again, the bike is completely covered by a large white sheet in the corner of Phoebe's room; however, in a later shot, the wheel of the bike is visible. (00:13:15)
The One With All The Candy - S7-E9
Visible crew/equipment: After Ross gives Phoebe the bike and she is leaving to ride it for the first time, the stage lights are visible in the rear view mirror.
The One With All The Candy - S7-E9
Continuity mistake: In the scene where Monica's female neighbour comes begging for candy, after Monica gives it to her and shuts the door it's a man standing at the door not the neighbour.
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 With the Holiday Armadillo - S7-E10
Continuity mistake: During this episode, Chandler is having major problems slipping people dollar bills. He asks Monica if Richard (her ex) use to slip people notes. But in Series 2 there was an episode where Chandler and Joey were doing impressions of Richard; they impersonate him by slipping money to each other with no problems. So not only has Chandler forgotten that Richard used to slip money, he's also lost the ability to slip money himself. (00:05:05)
The One With the Holiday Armadillo - S7-E10
Continuity mistake: When Ross is on the couch telling Ben about Chanukah, Ben's hair varies from shot to shot. In the first shot it's flat and in the next shot it's spiked up at the front. His hair stays spiked up for a few shots and then returns to flat. (00:06:00)
The One With the Holiday Armadillo - S7-E10
Revealing mistake: When Ben sits on the sofa to listen to Ross talk about the festival of lights, you can see Monica move Ben to the other side of the sofa despite there being space for her to sit. This is so they sit in the correct order as she would mask Ben to the cameras.
The One With All The Cheesecakes - S7-E11
Continuity mistake: Phoebe and David see each other at the coffee house and start talking. The buttons on Phoebe's red cardigan go from gaping to properly shut a number of times throughout the scene. (00:09:30)
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.