Donnie Wasn't Real?

Rolling Stone interviews Steve Buscemi about The Big Lebowski and Buscemi lets this little gem out.

I don't know how big this is but there's this new theory that Donny is just a figment of Walter's imagination. Like he's an old army buddy that had died or something. It almost works. There's the "your phone is ringin', Dude" "thanks, Donny?" [exchange]. But that's the only acknowledgement that the Dude makes of Donny. If you watch those scenes, it's like Donny would come in, Walter gets so upset and it's like the Dude never hears it.

Very interesting. I need to rewatch it and keep this theory in mind. If you can delete that one scene, does the theory really work at all?