Continuity mistake: When Jack picks the wrong card, when his dad is playing "find the queen", the coat on the end of the bed changes position. (00:22:25)
Continuity mistake: At the beginning of the episode, Wills' scarf repeatedly changes from hanging loosely over his shoulders, to wrapped around his neck. (01:01:15)
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)
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 Beverley walks out of his hotel room to talk to Karen, he places a bucket with a champagne bottle in it, on the floor. In the next shot the bottle and white napkin are on the other side of the bucket. (01:15:10)
Continuity mistake: When Matt and Grace are drinking mint tea, when Jack comes into the room to borrow Grace, Grace's mug of tea vanishes from her hand between the shots. (01:17:40)
Continuity mistake: When Will runs in and takes a photo of Matt Damon and Grace kissing, to get evidence Matt is straight, when Jack pulls out the film from his camera, two boxes (a black and red one) vanish from the coffee table. (01:20:20)
Someone Old, Someplace New (1) - S4-E17
Continuity mistake: When Jack is making his film for Karen, as he's interviewing Grace, he holds a cheque book up to his mouth. Between shots the book randomly alternates from being in his right/left hand. (01:31:40)
Went to a Garden Potty - S4-E20
Continuity mistake: When Karen is talking with Norman about donating funds for his advert, and then when Jack enters, between shots during the scene Karen's pearl necklace keeps jumping in and out of her black shirt. (00:45:00)
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)
Continuity mistake: When Will and Gavin are at the gay club, they sit down at the table with their laptops. There is a bowl and a glass candle on the table, which change their position and even disappear in some shots. (00:14:00)
Hocus Focus - S4-E24
Continuity mistake: Before Fannie starts the photo shoot with Will and Grace, she unbuttons the top of Grace's trousers. But later on in the shoot you can see they're done up, then later on they're undone once again. (00:34:00)
Hocus Focus - S4-E24
Continuity mistake: After Fannie rips open Grace's shirt and ties the bottom into a knot, the way the knot is tied and positioned changes during subsequent shots. (00:34:00)
Hocus Focus - S4-E24
Continuity mistake: When Jack is stroking the rabbit that he thinks is Karen, the position of the mobile phone on the side next to him changes, and also a glass of drink appears next to him in one shot, but is gone in all others, previous and after. (00:41:05)
A Bunch of White Chicks Sittin' Around Talkin' - S4-E25
Continuity mistake: In the opening scene with Will, Grace, Jack and Karen, as they open the wine and talk about what they would like to accomplish in life, the newspaper disappears from the table during the scene, then reappears in a later shot. (00:47:30)
A Bunch of White Chicks Sittin' Around Talkin' - S4-E25
Continuity mistake: When we see Jack dancing at the open auditions, there is a grey sports bag behind him which alternates from propped up against the small black chair to sitting in front of the chair on the floor, many times during the scene. (00:52:25)
A Bunch of White Chicks Sittin' Around Talkin' - S4-E25
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)
A.I.: Artificial Insemination (1) - S4-E26
Continuity mistake: When the four are eating dinner and talking, Will says "Well I don't wanna sleep with you either," and in this closeup Karen picks up her glass of wine. In the next shot the wine glass is back on the table and she's now holding her fork. (01:14:35)
A.I.: Artificial Insemination (2) - S4-E27
Continuity mistake: After Grace pushes Will, and he falls back and rolls over the bed, in the next shots the position and amount of rose petals on the bedspread changes, and the position of the pillows differs as well. (01:29:00)
Answer: A history of the game can be found at http://www.fast-rewind.com/bacon.htm.
J I Cohen