There was a rock and roll song from the late fifties or early sixties with the chorus:

Let me in, oh tender woman,
Let me in for heaven's sake!
Let me in, oh tender woman,
Sssssighed the snake.

The last verse, after the woman takes in the snake and feeds and cuddles him and he turns around and bites her:

"Shut up silly woman,"
Said the snake with an evil grin.
"You knew darn well I was a snake
Before you let me in."