HA! The original script by Akryod was SO different it would make your head spin!
It's set in the future and there are tons of ghostbusters. The movie made them bust about 30 giant ghosts and a couple of small class-6s. The Stay-Puft Marshmellow man came in page 80 or so. It was scrapped of course 'cause at that time it would have cost $300,000,000! VS. Our GB which cost $3,000,000.