Revealing mistake: After the opening credits there is a shot showing the house on the island where Karen and Stan live. If you look at the hanging chair, you can see that Karen is sitting in it. But in the very next shot she is in a meeting with Will, in a different outfit. This is a re-used shot from the previous season, which shouldn't be there.
Continuity mistake: When Grace is telling Will about his dad's affair, she mentions that he grabbed the other woman's ass when she brought him a packet of Goobers during the interval. The thing is, she sees them for the first time during the interval, and we see the conversation that follows. The mistress brings him wine, not Goobers, and he doesn't grab her ass.
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: When Will tells Grace that he is gay, there is a tray of finger foods on the table next to him, as he kneels on the floor. In the second shot, the plate is covered in cling film, but in shots before and after, there was no cling film.
Continuity mistake: When Karen arrives late to Mason's swim meet, Jack balls her out, and she stirs the Bloody Mary she's holding then throws the celery stalk down into the pool. Yet, two shots later, as Jack rides his scooter out, the long celery stalk is amazingly back in her drink.
Continuity mistake: When Grace tells Will that it is laundry day and that she has been wearing a peach bridesmaids dress all day, Will says, "Oh, um there's a roll of quarters in my top drawer right beside." When he says that he has a fork on his hand, when the shot changes he says, "My eye cream and my pedicure kit," suddenly the fork has disappeared.
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 Jack reveals to Will that he is too shy to ask out the sales assistant in the Banana Republic, Jack stands by a wooden shelf. Between shots the positions of his hands on the wooden pole keep changing, and which hand is holding it with also differs.
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.
Continuity mistake: At the club, Will is at the bar and he says "another round," and in the next shot a beer and a yellow Alco-pop drink is on the bar in front of him. In the next shot they've vanished, and the bartender once again places the same drinks down again for him.