Though the film was planned as a very low budget, bare bones production, enthusiasm and word of mouth about the script took hold and things changed. Roughly 300 people participated.
The exterior scenes were all shot on location at Universal Studios (that's Frankenstein Plaza in the opening shot). Most of the interior's were built on a sound stage at Universal as well.
The hearts in the butcher shop scene were, in fact, actual pig hearts. Far from being disgusted, the actors fiddled with them happily between takes.