A very honestly eccentric movie. It’s not a horror comedy, but with that title and concept it can’t be intended seriously either. Or maybe it was meant to be a horror comedy (early on, after dissolving a traveler inside its yellow-acid body, the bed eats a bottle of pepto) but forgot to write any jokes. Everyone acts stoned in this, so maybe that’s a clue.
The narrator is a guy who’s been dead for sixty years whose soul is trapped in a painting overlooking a bed, created by a demon to seduce a mortal girl, whom he accidentally fucked to death, and now the lonely bed feeds on hippies who wander in and sit on it, getting dissolved to bones. After a long period of hunger, it eats a bunch of hippies at once and finally falls asleep, which allows the guy in the painting to speak.
I guess the final girl who completes the ritual that banishes the bed is Susan, but there’s also a Sharon and a Diane, and I got them confused. Susan’s brother who gets his hands dissolved to bones was later in some proper movies, and the boy in the painting was apparently a famous rock critic, but otherwise everyone here including the movie itself vanished until the cult kids rediscovered it in the 2000’s.