Continuity mistake: The position of the high heels in the barrel, in the church bazaar differ greatly between shots as Karen enters the room, up to when she walks over to find her slingbacks. No-one else touched the shoes in between. They also change position as Karen kindly gives Sally some extra money. (00:57:25)
Continuity mistake: When Grace and Val sit and watch TV on the floor, between shots the wine bottle moves and a cork appears in the top of it. (00:24:40)
Continuity mistake: When Karen is laying on bed, looking at the leaflet Jack gave her, between shots her martini swaps from her left to her right hand. (00:26:40)
Continuity mistake: When Will and Grace sneak into Val's apartment to look for the music box, the number on the door is 12E. However, in Season 1, 'Grace Replaced', when Val and Will are talking in the elevator, she says she moved into 15F.
There but for the Grace of Grace - S2-E21
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)
There but for the Grace of Grace - S2-E21
Continuity mistake: When Shannon is asking Grace why she didn't go through with her marriage, there are three glasses of near-empty wine on the table. In one shot they all completely vanish, then reappear in the next shot. (00:55:40)
There but for the Grace of Grace - S2-E21
Continuity mistake: When Will and Grace are sitting at the dining table discussing how much like Sharon and Joseph they are, the napkins on the table change shape and move around a bit, and one ends up with a plate underneath it just before Will picks it up.
My Best Friend's Tush - S2-E22
Continuity mistake: When Jack is talking to the board manager about kicking Will out of the 'Subway Tush' invention, confetti on Jack's shirt front disappears then reappears, and the confetti on his shoulders differs as well. (00:10:40)
My Best Friend's Tush - S2-E22
Continuity mistake: When Jack throws the butt-puppet at Will, and storms out of the room, one of the pantyhose legs unravels and hangs down. In the next shot it's shorter and wrapped back around. (00:13:30)
Continuity mistake: When Will and Grace have dinner with Ben, in one shot Ben begins to lift his wine glass up, but in the next shot it's back on the table. Later on the wine glass jumps into his hand as well. (00:47:35)
Answer: A history of the game can be found at http://www.fast-rewind.com/bacon.htm.
J I Cohen