Continuity mistake: When the guy at Will's party tells everyone the beer has gone, everybody leaves, and the guy puts his plastic cup on the handle sticking out from the keg. In the next shot the cup has suddenly gone, then reappears again in the next.
Continuity mistake: In the scene in which Will is sitting in Bobbie Adler's bathroom, talking to Jack on the telephone, the shots alternate between the bathroom and Jack's bedroom. At the beginning of their conversation, the digital clock in Jack's bedroom reads 12:07. For the next few shots, each time the audience is taken back to Jack's bedroom, the time on the clock has changed according to the actual time lapsing in the scene. However, in the middle of this sequence, the digital clock suddenly reads 12:24, where it had read 12:09 in the shot immediately preceding. Finally, in the very next shot in Jack's bedroom, the clock has gone back to "real time," with a reading of 12:10. The assumption is that the shot in the middle of this sequence had to be re-done, thus reflecting the time passage on the clock.
Continuity mistake: When Will phones Jack, while he hides in the bathroom, Jack puts a plate of chicken down and answers the telephone. Then through the following conversation they have the position of the fried chicken pieces on the plate differ.
Continuity mistake: When Will stops Grace, as they are about to have sex, they sit up in the bed, and he tells her he thinks they should wait. In the first shot Grace's black strap is falling off of her arm, yet in the next shot it's back up on her shoulder.