The Coen Bros are known for being inspired by classic literature. While, officially, The Big Lebowski is mirrored after the novel The Big Sleep, there are some clear connections to another great book -- The Wizard of Oz.
The Wizard: A phony, a faker, a goldbricker who acted like a mage but in truth was just a little man hiding behind a curtain. Jeffrey Lebowski acts like a rich man, but the truth is, he doesn't have any actual cash. He's a fraud.
Dorothy: Bunny Lebowski is a girl from the Midwest, from the farm, who's trying to find her way home. Okay, she may not be sweet and innocent, but she is your modern day Dorothy. They even gave her a little Toto yipping at her feet.
Cowardly Lion: The Dude lacks courage. Courage to take control of his life, to confront others. In conflict, he backs away. He's The Dude, man.
Tin Man: Donny, of course. He's in need of a heart.
Scarecrow: Walter is like a scarecrow. He puts up a front as a scary individual, something to be fared. But really, he's all talk. And, let's face it, he needs a brain. Also, pretty sure the Scarecrow was Jewish.
Flying Monkeys: Nihilists. 'Nuff said.
Yellow Brick Road: The term "goldbricker" is used quite often. Gold bricks? Yellow bricks? Sure!