In terms of status, the quick description of director Dwain Esper is that he was the Ed Wood of the 1930s, and the berserk, entertainingly out-to-lunch Maniac is certainly his Plan 9 From Outer Space A scientist works on a method for raising the dead and he’s obsessed to the point that he’s gone insane. His assistant, an aspiring actor who also happens to be on the run from the law, is forced to aid the scientist in stealing corpses and human organs under threat of exposure. The assistant eventually has enough of that and he kills the scientist and, to cover it up, uses his acting skills to pose as him. He gets so into the character though, that, like the scientist, he also begins losing his mind.
The famous scene is when he grabs hold of a stray black cat whose presence around the lab has been picking at his fragile mind (a situation borrowed from the Edgar Allan Poe story), pops out one of its eyeballs and then eats it. The scene with the patient who thinks he’s a gorilla will also stay with you ’til your dying days.