Sid Haig was an American actor known for his parts in Jack Hill’s exploitation fare (Spider Baby (1968), Coffy (1973), Foxy Brown (1974)). He also had a part in THX 1138 (1971), the science fiction film directed by George Lucas in which in a dystopian future the populace is controlled through mandatory use of drugs that suppress emotions.

Cult Movie Stars (1991) describes Haig as:

“Ugly, ruddy faced, usually bald, and occasionally bearded — he looks like an original member of Frank Zappa’s Mothers of Invention — Haig has been a seedy presence in low-budget, sex- and action-packed drive-in movies since the mid-sixties.”

Above is Spider Baby (1968) in which Haig is Ralph, one of three inbred, demented, and dangerous siblings. Ralph is a sexually advanced, but mentally deficient simpleton who moves through the house via the dumb-waiter. Unable to speak, Ralph communicates with only grunts and leers.

The siblings are introduced by their guardian as:

“Well, no. It’s more than a retardation. It’s sort of a regression, a progressive deterioration of the mental faculties, a rotting of the brain, so to speak. It begins in late childhood and progresses rapidly, ultimately resulting in physical deformity, rather like the last stages of paresis […] The unfortunate result of … inbreeding.”

The full film is on YouTube.