It was a graveyard smash.
Mid-century movie horror and early rock and roll shared an operating principle: they were safe, marketable ways to explore and play with the transgressive. In their safest forms, they are the spirit of carnival.
Groovy monsters are best suited for children, who are interested in horror and rock and roll but don’t really know much about the details of either.
Halloween is the most rock and roll of children’s holidays.