Sex and Zen (1991)

A recently married scholar goes on a quest for knowledge of other people's wives, based on his philosophical differences with the Sack Monk. He encounters the Flying Thief, who agrees to help him find women, but only if he attains a penis as big as a horse's.

This is definitely not the kind of soft core porn that you would find being made by western cinema. Primarily because the story is almost complicated, but also because it features a horses dick as the key to the plot, with even enough thought gone into this scenario that our hero can't get a boner unless he sees flowing red material as the horse supposedly did.

It is the source of quite a few sequels, even spawning 3D Sex And Zen: Extreme Ecstasy in 2011, however none of them can match the obscure originality of this humorous classic.