The Superhero Club at Facebook ran images of Marvel's Avengers through FaceApp to change their gender. The results look eerily believable -except for the Hulk, who is always a cartoon.
The app changes facial dimensions slightly, like widening the cheekbones for females and narrowing them for males. It also adds makeup to female versions, and removes it for male versions. You might notice that when changing a male superhero into a female, the app removes ten years of age. When changing a female into a male, the two characters look the same young age. You can see all 14 of them in a post at Geeks Are Sexy.
While the characters look like the same person or siblings, I could swear that the female version of Captain America is an actress I've seen somewhere.