I think I figured out how they came up with the idea for this movie.
Asylum founders David Michael Latt and David Rimawi are hanging out one night and decide to watch a movie. Magnolia is showing on HBO, and since neither one of them has ever seen it, they decide to give it a chance. They wake up two hours and 40 minutes later, when the film is in the midst of it's frog-raining climax.
Latt: Huh? I didn't see that coming.
Rimawi: Me neither. What was this movie about again?
Latt: Dunno. I guess frog rainstorms or something.
Rimawi: Huh. Hey, you know what would be even better? A movie where it rained sharks!
Latt: Hell yeah! But wait... what if, instead of raining sharks, they where flung through the air by a tornado?!
Rimawi: BRILLIANT! WE MUST MAKE THAT MOVIE!