Revealing mistake: When Grace steps on the Dance Dance Revolution machine, she positions herself in a way it looks like she's playing on Double Mode, but the on-screen arrows in the game clearly show that she's playing on Single Mode.
The Truth About Will & Dogs - S1-E10
Continuity mistake: When Karen was at Will and Grace's flat with Jack babysitting the puppy. She puts her cocktail glass down on the table and leaves, but when Will and Grace come back from the movie there is no glass on the table. (00:36:50)
Fagmalion Part Four: The Guy Who Loved Me - S5-E19
Continuity mistake: When Will enters Barry's apartment with the big brown bag of Chinese food, he walks over to the chair and puts it down. On the table is a magazine laying parallel to a book. A shot later the magazine sits vertically to the book.
A Gay/December Romance - S6-E12
Continuity mistake: After Grace drops her take-out container of Happy Noodles, in the restaurant, the position of the container on the floor changes between shots from laying down to on it's side. (00:06:20)
Visible crew/equipment: As the chorus director says he wants to do the song again because "this Owen Person" didn't show up for his callback, there is a whole boom dipping into view. (00:05:35)
Continuity mistake: When Karen and Jack are in the Barney's window room, the door is open. When they leave, it is closed. (01:07:20)
Continuity mistake: After Will and Jack unwrap their breakfast, Jack puts the wrapping that the Smart Start cereal box was wrapped in, on the table. In following shots the wrapping keeps changing position, from spread out, scrunched up, etc.
Acting Out - S2-E14
Continuity mistake: Jack's scarf keeps changing position as he is riding his bike alongside Will and Grace, down the street. The scarf repeatedly alternates from behind/in front of his shoulder. (00:00:35)
It's the Gay Pumpkin, Charlie Brown - S5-E5
Continuity mistake: In the scene where Grace is fixing her bike chain, there is black line going across her cheek. The shape and size of the line changes several different times.
Continuity mistake: As Karen and Beverly play snooker, and are trying to pot the black ball, the positions of all the little blue cube-stick chalks keep changing. They jump onto the table/onto the tableside between a few shots. (00:35:10)
Marry Me a Little More - S5-E9
Continuity mistake: When Jack is trying to prepare his wedding speech, he taps some wine glasses, which smash. He then puts them on the piano. In following shots the wine glasses, spilt wine and broken glass on the piano changes position / (dis)appears.
The Young & the Tactless - S3-E21
Continuity mistake: The position of the serviette which Jack throws down onto the table, during breakfast, when he goes to talk to Karen, changes during shots.
Continuity mistake: In the episode "Grace, Replaced", with the neighbor Val who moves into "apartment 15F" in the same building as Will and Grace. Yet in the previous episode "Yours, Mine or Ours" with Peter (who moved into 12D) we learn that 12 is the highest floor in the building...
Continuity mistake: After Dr. Hershberg makes the joke about the small cup of urine, he places it down on the side by the small equipment table, yet in later shots you can see the cup on the side by the door. (00:06:00 - 00:08:20)
Continuity mistake: When Will and Grace are standing outside Will's apartment, after Grace arrives back from her honeymoon, Grace is holding a handful of photo envelopes. Between shots the way she holds these envelopes changes.
Continuity mistake: When Jack is trying to hush the audience at his show Jack-Talk after bringing Grace onto the show for a follow-up interview, between shots the little bell on his desk moves from his right (near the edge) to over past his left, near the centre of the desk with all the other items. (00:15:55)
He Shoots, They Snore - S4-E21
Continuity mistake: When Grace is setting up her design class, she writes "Professor" on the board, and curls the end of the R into a spiral. But in the shot when she says "T.A. - Teachers Assistant" the spiralled end on the R has gone. In the next shot it's back again. (01:04:40)
The Truth About Will & Dogs - S1-E10
Visible crew/equipment: Jack and Karen are sitting on the couch, and Grace says, "come on, let's go." There is a boom mic visible at the top of the screen, it rotates towards Grace. (00:14:38)
Visible crew/equipment: As Will talks with Jack about the marriage to Rosario, the studio behind the cameras is reflected on the silver set piece behind Will.
With Enemies Like These - S11-E3
Continuity mistake: Sharon Timmer introduces herself to Grace in Series 10 Episode 1: "I've lived directly below you for 19 years." But then in Series 11 Episode 3 she seems to live in Flat 9B next door to Will and Grace. I'm not sure we've ever seen who lives there before, but guessing by the layout of Will and Grace's flat, there wouldn't actually have been space for an extra flat in that space. (00:00:16 - 00:12:12)
