The Japanese version wasn't Fukasaku's "preferred cut"; THE GREEN SLIME was a contract job for Fukasaku, and he worked on the film with other Toei house directors on it. Since he was the lead, his name was slapped on the credits. The Japanese version was short because it was a part of a "Toei Cartoon Parade" kiddie matinee lineup, and the running time was compressed to accommodate several animated shorts to fill out the package.