The performer was Shari Lewis, and Lamb Chop was her sheep hand puppet. The show was the unimaginatively titled The Sherry Lewis & Lambchop Show. Ms. Lewis, who has reached the clearing at the end of her path, was probably as far removed from "one sadistic asshole" as she could possibly have been.
Presumably Saint Peter had words with her about this ditty at the Gate, however. Maybe she's still standing there singing it today...