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Nightmare Fuel: Rockos Modern Life
One character is a foot with a face on it.
And one is named Captain Compost Heap.
"YOU PUT ME IN A JAR?!" What. The. Hell.
The episode in which Heffer choked on chicken and Rocko had to enter his body to find his heart and restart it. Of course, Heffer's insides were as creepy as could be, and his heart was a realistic heart.
The end of the Fortune Cookie episode really screws with a young mind.
The Hopping Hessian episode really did a good job of being surprisingly unnerving for a kid's show.
The episode "Who's for dinner" had Heffer's house which was a family of wolves who were carnivores. Carnivores who are eating what is obviously completely sentient food. Rocko opens up a mirror in the bathroom, which reveals three pigs tied up and gagged, and Rocko responds by merely closing the mirror to leave them to their fate.
There's also the room full of girls who look like Red Riding Hood.
Rocko slammed the mirror shut on obvious impulse and looked horrified at what he saw, which doesn't seem to fall in line with someone "leav[ing] them to their fate." He could, y'know, open it back up again.