The Warehouse (South Park)

It was a cold, Halloween night when the boys met up. They gathered before a warehouse, a scientific warehouse. Seeking out to get some cheap thrills and good scares, they enter the facility which once belonged to Dr Alphonso Maphesto, who's presumingly been dead for years. While they're just wanting to have some fun, to possibly see some dead, mutated animal carcasses it seems they've bitten off more than they can chew upon entering.

There's not just dead animals, but slowly decomposing, foul smelling, deceased humans too.