Indiana Jones and the Men from Mars (or something along those lines, I forgot the actual title)
The full original title was "Indiana Jones and the Saucer Men From Mars. Seriously. Lucas meant for it to be an homage to bad 50's era sci-fi movies, but when he first pitched it to Spielberg and Ford, they just looked at him and asked "Seriously, who's your dealer, I want what you're smoking" (not really, but that was the gist
), and they instead went for the homage to rock'em-sock'em 30's-40's era "Cliffhanger" type movies.
My friends have warned me away from this, and I think it would ruin the happy memories I had of The Last Crusade. That was my last Indy movie, I cannot recognize this, especially since Lucas had too much of a hand in it.