It was about a boy who gets turned into a cobra/human and displayed either at a circus/carnival or a science park. A mad scientist injects the boy with a serum, and by story end, he's a man-serpent.

One of the actors, can't currently recal his name, was also in Cool Hand Luke, If I recall correctly.

Strother Martin played the mad scientist in Sssssssss and had his famous line about a failure to communicate in Cool Hand Luke.

And the guy who became the snake was Dirk Benedict, later to be on the original Battlestar Galactica as Starbuck.

And the daughter was one of the little brats in The Sound Of Music.

The mad scientist has a beautiful daughter. She brings boyfriends home. He turns them into snakes.

John

It sadly never became an episode of MST3K but I remember watching it on cable and talking all the way through it like it was.