I'm showing my age here... but waaaay back in the dark ages (OK, the 1980s) Marvel Comics had a character named 'Cloud' who used to appear as either a male or female humanoid depending on the mood they were in. The character was a nebula that arrived on Earth and took on the forms of two different humans (a young couple who had died), so they could choose to present themselves as either male or female.
Cloud started out in the Defenders back in 1983, and I remember reading stories where the other characters were surprised to have said goodnight to a female Cloud at night, and when they come downstairs in the morning Cloud had shifted to male form just because they felt like it. And I remember thinking that that seemed like an amazing thing to be able to do.
Cloud went through a sort of puberty and started becoming attracted to people, and it was interesting to see the same character attracted to the same people whilst presenting as two different sexes. Pretty ground-breaking stuff for the era, if you ask me. As I recall, their behaviour was pretty much gender-neutral most of the time, although Marvel did experiment with Cloud behaving more stereotypically female whilst in female form, and more male whilst in male form.
The character was drawn pretty much naked apart from a few wispy bits of cloud covering the interesting bits, so I'm not entirely sure it's appropriate to post an image here.
