Some of those alt-castings are awesome, but some are total wtf.
Luh-huv the concepts for Drive, The Hangover, 2001, Terminator, and Trainspotting....and Zappa is awesome for The Dude....
...but....seriously wtf:
Bowie as Walter Sobchak? Nimoy as John McClane? John Wayne as Superman? And Belafonte as Jules? *Everybody* knows Jules should be played by Sidney Poitier.