When Phoebe goes into Joey's apartment and find Rachel playing the drums, the door behind Phoebe is closed. When Phoebe leaves, after Rachel and Joey play the 'Tequila' song, the door is open again.
When Chandler says "Hey, Pheebs. If you wanna get Joey a Christmas present that disrupts the entire building...", he is messing with his tie and as the camera angle changes, it is no longer in his hands.
The three Chanukah candles are in the menorah lined up from the left. They should be lined up from the right.
Rachel claims not to be afraid of the tarantula because she had one as a child, but when she puts the drumsticks into the cage with it, she obviously does it very quickly and closes the lid even quicker out of fear.
Chandler asks Monica how she knows about slipping money to the receptionist to get seats. He and Joey already knew this in earlier episodes, particularly in the early episodes with Richard (Monica's then-boyfriend).