C.S. Lewis and L. Frank Baum were having a good laugh after having read Phillip Pullman’s His Dark Materials trilogy. When they finished wiping their eyes, they then decided it was time to collaborate on a project own. They worked out the rough draft and after having gotten a few notes from Frank Herbert and Madeleine L’Engle, plus a suggestion or two from Baron Munchausen. They dropped the completed story off in John C. Wright’s head.
The result is a mind bogglingly great novel called; Somewither.
I highly recommend it.