It's like someone had planned a whole bunch of teeny slasher movies, but he didn't have the budget for it so decided to take the all the killers/monsters and put them into a single movie.

I vaguely remember this from the video store in high school. Five for hazily recollected nostalgia over crap movies?

Went ahead and looked through the movies I've uploaded for dead tags that may catch your eye:

dont just stand there idiot!
fanservice
innappropriate wanking

Perhaps "12 angry men" would work because there's 12 monsters?

Owing to the number of lazy ethnic stereotypes used as monsters I'm going to propose the missing thirteenth monster was all in blackface, wore a battered tophat with white gloves and was called King Cotton.
This sadly meant they had to cut out the scene where he throws a hapless pair of copulating teens into a 'gin.

Bart trains with tan walls. That's one way to cover up the urine.

I'm not sure which one I'm least scared of.