The One With All The Resolutions - S5-E11
Continuity mistake: Rachel mentions "the big thing," so Joey sticks his fingers in his ears to block her out. When Rachel pulls on his arms, the only things on the table are Joey's bottled drink, crayons, and coloring paper. In the next shot, we see Rachel's arms and she's not holding anything. It cuts to the next shot facing Joey, as he says, "Well then, it wouldn't be a secret, so yeah, that would be OK," and now there's a drinking glass on the table. Rachel removes it in the next shot.
The One With All The Resolutions - S5-E11
Continuity mistake: At the start, when the countdown hits 3-2-1, there's a closeup facing the TV, and in the TV's reflection the couch and armchair are both quite empty, but in previous and following shots both have people seated.
The One With All The Resolutions - S5-E11
Visible crew/equipment: Monica and Chandler leave the apartment to go "do laundry," then Phoebe heads out to the airport. When Joey takes a seat, the reflection of camera movement is visible on the window, above the sink. Then Rachel and Joey tell each other they can't share what they each know, and just as Rachel sits down beside Joey, once again we can see the reflection of camera movement above the sink. (00:19:30 - 00:20:20)
The One With All The Resolutions - S5-E11
Visible crew/equipment: After his fiasco with the leather pants, powder, and lotion, when Ross is at Monica's and tells the others he's going to kiss Ben goodnight, as he starts walking to the bedroom the camera can be seen at the right side of the screen.
The One With All The Resolutions - S5-E11
Continuity mistake: When Joey and Rachel are trying to work out if the other knows about Monica and Chandler, they sit at the table in silence. In a side shot of Joey they look at each other sneakily, and Joey has his arms by his sides. It then cuts to a head-on shot of Joey, and he's got his right arm over the back of the chair. (00:19:00)
The One With All The Resolutions - S5-E11
Continuity mistake: When Ross first enters Elizabeth's bathroom, the lotion is first in line on the shelf; next to it is something else and then the powder. Later, the powder is first in line on the shelf and the lotion has moved. (00:09:30 - 00:12:45)
The One With All The Resolutions - S5-E11
Continuity mistake: During the countdown to midnight, just as everyone says, "Happy New Year!", the camera cuts to Phoebe and Ross. In the background Joey and Rachel open their arms to hug each other; the camera cuts to just Joey and Rachel and they open their arms again. (00:01:00)
The One With All The Resolutions - S5-E11
Character mistake: In one of the scenes where Phoebe is teaching Joey guitar, she asks him to demonstrate the "Iceberg" chord. To refresh his memory, Joey refers to the chord as "G Sharp." In reality, the only way to play a G Sharp chord is with a barre chord, and as such the fingering is not exclusive to it.
The One With All The Resolutions - S5-E11
Continuity mistake: Immediately when the opening scene starts, we hear from the crowd on the television that there is less than 60 seconds to midnight. However, 60 seconds later in the scene, the countdown still hasn't reached zero.
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.