The “homework found in the back seat of a stolen car” plotline is a true story, as well
The “homework” scene, also known as the “Find a Stranger In The Alps” scene, thanks to the absurd censorship the film receives on basic cable, is one of the most iconic in the film. Once his stolen car is recovered, the Dude finds homework he believes belongs to the car thief in the back seat. This sends the Dude and Walter Sobchak (John Goodman) on a wild goose chase that winds up with two cars destroyed and the protagonists gaining nothing in their search for the truth behind the kidnapping/ransom. As bizarre as it sounds, it’s also loosely based on a true story, and points to the real life person (or at least one of them) Sobchak was based on.
Walter Sobchak is an amalgamation of a few people the Coen brothers have known, but many traits were generously borrowed from the life of Paul Exline, the man who greenlit the 1987 Coen brothers film Raising Arizona. He did have a car stolen that he had to track down to the impound lot. He did find a kid’s homework in the car, and he brought along his friend to interrogate the kid. He even put the homework in an evidence-like bag and wore a suit to more fully play the detective role. The house was even owned by an elderly man in an iron lung.
However, there’s no mention by Exline of crowbars or his opinion of Alpine strangers, which is probably for the best. Some things are best left a mystery.