The One Where Rachel is Late - S8-E22
Continuity mistake: The first time Phoebe and Monica are making bets on when Rachel will give birth, Phoebe has a bottle of water in her hand and is holding it near her stomach. She puts it to her mouth to drink some, but in the next shot, the bottle is near her stomach again. (00:07:00)
The One Where Rachel is Late - S8-E22
Continuity mistake: In one scene, Rachel is using the bathroom. She yells out to Monica and Phoebe "Whose turn is it to help me get up?" A few scenes later Rachel goes to the bathroom again, but gets up with no one helping her. (00:07:05)
The One Where Rachel is Late - S8-E22
Continuity mistake: At the end, when Rachel and Ross leave for the hospital, Rachel grabs the keys. In the close-up, when Rachel asks, "Do you think we have time?" she holds the keys up in her left hand while Ross holds her empty right hand. It then cuts to a medium shot, and the keys are now in Rachel's right hand, the same hand Ross holds. (00:20:40)
The One Where Rachel Has a Baby, part 1 - S8-E23
Continuity mistake: At the beginning, when Rachel first arrives at the hospital, she is talking about the hospital not being out of rooms. She points to herself with her right hand saying 'What if I was the president?' Then when the shot changes to include Ross she is pointing to herself with her left hand, then it cuts back to just Rachel and she is using her right hand again. (00:01:25)
The One Where Rachel Has a Baby, part 1 - S8-E23
Continuity mistake: When the couple who has bad pet names for each other is sharing the maternity room with Rachel, the man is unpacking a suitcase that he closes, but in the next shot its open and he flips the top closed again. (00:09:10)
The One Where Rachel Has a Baby, part 2 - S8-E24
Continuity mistake: When Ross is telling Chandler that Janice is there and she's contracting Chandler can be seen putting his hands on his face. In the very next shot his hands are by his side again. (00:02:50)
The One Where Rachel Has a Baby, part 2 - S8-E24
Continuity mistake: While Rachel is having her baby she grabs Ross by the shirt and says 'you do it for me' in the next shot her hand is no-where near Ross. She couldn't have put her arm down that quickly. (00:33:50)
The One Where Rachel Has a Baby, part 2 - S8-E24
Continuity mistake: When Phoebe and Ross are standing in front of the screen looking at all the babies and talking about why He and Rachel aren't together, some of Phoebe's hair is in front of her shoulder on the right hand side then the shot changes looking over Phoebe's shoulder at Ross. Then when you see Phoebe again her hair is behind her shoulder yet she has not moved or touched her hair. (00:45:00)
The One Where Rachel Has a Baby, part 2 - S8-E24
Continuity mistake: When a nurse is putting Emma to bed we see that Emma is nicely wrapped up in a blanket. The shot then cuts and Emma's right arm is sticking out the top of the blanket.
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.