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 Definition of Marriage (1) - S8-E15
Revealing mistake: At the very start when Will enters the coffee shop, he walks over and asks the server for a coffee. The server picks up a mug, pretends to push the coffee machine button, holds the mug under the machine for about two seconds and hands it to Will. To top it off you clearly see nothing go into the mug. (00:00:05)
Revealing mistake: In the scene when Will brings out the turkey, Karen clearly says "my God, this scene is so long!" Apparently Megan Mullally said it on every take due to the length of the scene and the amount of times they had to reshoot it.
Revealing mistake: When Grace and Will are looking at the large tin of Protein shake powder, you can see there is tape covering all of the logos and brand name on the tin. (00:21:45)
Answer: A history of the game can be found at http://www.fast-rewind.com/bacon.htm.
J I Cohen