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Moria says, "the film is a whacked-out dive into dementia. It could be described as an Addams Family played seriously." 1000 Misspent Hours says,
What makes Jack Hill’s movies such a joy is that no matter how grim and horrid the subject matter becomes, he almost always retains a sense of warped humor about it, yet no matter how goofy and campy things get, he also invariably keeps his cutting edge. Spider Baby is among the blackest of black comedies...
Images Journal praises the acting and calls it "one of the great low-budget horror/comedies." Slant Magazine says, "it's unclassifiable, which has amplified its cult appeal." DVDTalk calls it "a creative and affectionate nod to chiller films, produced on a shoestring yet fashioned with care and imagination."