I can think of a couple of verses that celebrate polymorphous perversity:

Tom came home at his journey's end
To find his wife in bed with a friend.
The night was cold and the blankets thin.
"I'll sleep in the middle" says Tom Bolynn.
(Probably added by Oscar Brand)

Great joy they reap from tupping sheep
In sundry bogs and ditches,
Nor care a damn if it's a ram --
Those hardy sons of bitches!
("The Pioneers")