Continuity mistake: When Ben is mixing the salad with Karen, Karen walks away, and one of the wooden spoons they were mixing with falls onto the worktop. In a following shot the spoon has suddenly jumped back into the bowl so that there are two in the bowl, then in a later shot the spoon vanishes once again. (00:54:25)
Continuity mistake: When Dr. Hershberg is crying after giving some bad news, he knocks a grey box off of the small equipment table which he is leaning on. Later during the scene the box suddenly jumps back up onto the table. Also, the other items on the table jump around and change position on their own accord a few times. (00:05:00 - 00:07:00)
Continuity mistake: When Karen is talking to the security camera in the cell, before receiving the phone call from Stanley, the pieces of salami strewn all over the bed change and some pieces disappear, most noticeably one piece on the pillow. (00:57:30)
Continuity mistake: When Jack and Sissy are sitting in his apartment, discussing what they've done with their lives, they both have mint cookies that they eat while they talk. The bites and size of their cookies, most noticeably Sissy's, change between shots.
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. (01:16:40)
Plot hole: In the bowling alley scene, Ellen states that Grace would need to knock down 27 pins in order to tie. Will and Grace then have a conversation, and Grace gets a strike with her next ball. They then start gloating that they have beaten Rob and Ellen, but the scores don't add up, and they couldn't go into the lead on that round.
Continuity mistake: After letting Campbell out, Grace pulls the white blind down the door, and it stops about halfway down the door, and gets stuck, and is still rolled at the bottom. In the very next shot, the white blind is now unrolled all the way down perfectly. (00:07:00)