When Rachel is listening in on the phone to Monica and Chandler making romantic plans, she shrieks loudly just before pressing the end call button, yet Monica and Chandler didn't hear her.
When Ross comes out of the bathroom with no pants on, Elizabeth walks to the edge of the frame. After she turns around, she can been seen lifting up her hands, but in the next frame, she repeats her actions.
Ross is standing when talking about leather pants with fringe all down the sides. In the reaction shot of Chandler, he is sitting down. Then when they cut back to Ross, he is standing again.
After Chandler loses the bet to not make fun of anyone, he says to Phoebe, "Pheebs, flying a jet? Better make it a spaceship so you can get back to your home planet." Chandler wasn't in the room when she said she was going to the airport to wait for someone to leave a plane unattended.
At the start of the episode, the time between the moment Ross calls out "thirty-one" and everyone calling out Happy New Year is actually thirty-five seconds on screen.
At the end of the episode, Phoebe says that she couldn't go outside because it was raining.
But it can be clearly seen through Monica's apartment window that it was clear outside.
When Phoebe asks Joey to do the hand formation for "iceberg" the name she gave a particular guitar chord, Joey says to himself, out loud, "G sharp". Phoebe then asks if he's been studying the real names of chords. G sharp is not a real guitar chord. Guitar chords don't have sharp versions, only flat.
(at around 6 mins) When Rachel is bragging to the group about resisting gossip, the camera is out of focus. It re-focuses a few seconds later.
When Rachel is trying to get Joey to tell her about Chandler and Monica, she sits down at the table and when the shot pans down you can see the reflection of the camera and a light in the kitchen window pan down a second or two after.
When Rachel and Joey are loudly sharing that they know about Chandler and Monica, Ross is just in the other room with Ben, making it very possible that he overheard and also found out about Chandler and Monica.
Phoebe says that she doesn't know the actual names of the chords, but in other episodes she uses the real names of the chords. For example, in The One with the Baby on the Bus (1995), Phoebe talks to guest star Chrissie Hynde about what chords she knows, and she uses the actual names of the chords when she does this.
Joey (Matt LeBlanc) is trying not to laugh after saying "You don't know" to Rachel (Jennifer Aniston). After saying it he smirks, and then puts his hand to his mouth.
When Ross tells about the date with Elisabeth Hornswoggle, Joey doesn't react to the name at all and instead of that Chandler has a hard time not to make a joke about her funny last name. However, in the episode The One with the Pediatrician (2002) Joey can't stop laughing at Dr. Wiener, Sandy Poopack and Lana Titwyler.