Dwain Esper's notoriously awful exploitation film about an ex-vaudeville actor who assists a mad scientist to reanimate corpses and then goes mad himself is absolutely full of cats. Not only is what passes for a plot little more than a ripoff of Edgar Allan Poe's "The Black Cat" but "Maniac" is full of atrocities committed against our feline friends.
Lots of badly framed cat fights mirror later human "cat fights" involving scantily clad girls.
The scientist's neighbour claims to have literally thousands of cats in cages which he says he breeds for their skins!
And, infamously, the completely insane Don Maxwell (William Woods) gouges out a cat's eye and eats it! Fortunately, the eye (as you can see above) is a very fake looking human one and the one-eyed cat shown briefly in the film was already like that when he came from an animal shelter. It's still a nasty scene though.