Trivia: At the beginning of the movie, when The Dude is writing a check for the cream at the grocery, look at the date on the check. Sept 11, 1991. A few seconds later we see George Bush Sr. talking about Iraq. So here we have a scene containing Sept. 11th, George Bush and references to the Middle East in a movie that takes place in 1991.
Trivia: This isn't really a mistake, just something to note - throughout the whole movie the Dude is not seen bowling once. Also, every time you see Donnie (Steve Buscemi) bowl, he gets a strike, except for the last bowling scene, he does not get a strike, and he dies of a heart attack a few minutes after this.