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. (00:03:00)
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.
Trivia: A majority of the clothes The Dude wears are Jeff Bridges' own.
Trivia: In the original script, the Dude's source of income (in order to explain his nice apartment despite being unemployed) was going to be briefly explained - he was related to the inventor of the Rubick's Cube, and was living off an inheritance. It was eventually deemed unnecessary, and thus removed.
Trivia: The Dude is kicked out of the cabbie's car because he hates the band "The Eagles." The Dude's bowling rival Jesus was introduced much earlier in the film with a Spanish-language version of The Eagles song "Hotel California" playing in the background. One of those many nice details you don't necessarily notice the first time you watch that subtly ties the movie together.
Trivia: Woo and the other guy who work for Jackie Treehorn trade outfits when they come back to tell the Dude that Jackie Treehorn wants to see the deadbeat Lebowski. (00:03:50 - 01:13:50)
Trivia: Walter's look and personality is based on director John Milius, who helmed the original "Conan the Barbarian." He's a friend of the Cohen brothers, and evidently is as loud-mouthed, bombastic, overbearing and loyal as Walter in real life.
Trivia: In the "dream sequence", after Maude had her assistant knock out the Dude to steal back the rug, there's a scene shot from inside a rolling bowling ball, which reveals that Maude threw that ball. Use frame-by-frame and you'll recognize the hairdo, the green gown and the high boot.
Trivia: The couch and armchairs in Maude's Studio are by LeCorbusier, a historical person who to this day is held in contempt by critics due to his ties to fascism and anti-Semitism.
Answer: Themmen plays a background bowler in pretty much all of the bowling scenes. I don't know if this is necessarily worth a credit, but I guess his agent disagrees with me.