In Norse myth,
Loki is a shape-shifting god who enjoys the occasional turn as a woman.
The gender bender doesn’t discriminate; sometimes he’s even a female animal. In fact, Loki was once mounted by a stallion.
He then gave birth to an eight-legged horse. So when comic book writer Al Ewing wrote on Tumblr that the character would be bisexual (both in comics and films) and that he would “shift between genders,” it wasn’t a huge surprise.