The mist creatures of the planet Spermula transform themselves into beautiful women, so they can come to Earth and drain human men of all of their sexual fluids, in the amazing movie Spermula. And it's just possibly NSFW.
Actually, Spermula is a weird mixture of extreme campiness and artsy beauty. There's a random subplot involving a troupe of circus performers, who include a little person as well as a contortionist whose only trick is that he can pleasure himself. But then you get this weirdly gorgeous sequence where the Spermulites use telepathy to ensnare a priest:
And then there's this weird sequence where they turn a human woman into one of them, by "dehumanizing" her and converting her into a sperm-draining creature:
All of the Spermulites are supposed to be turned into beautiful women, but one of them is turned into Udo Kier by mistake. And he has an incredibly tiny penis, which everybody refers to constantly. (Seriously, every scene he's in, they bring it up.) Here he is, pleading with the leader of the Spermulites to give him a bigger penis. I love the part where he insists that he was made for physical pleasure: