Ever since Robin was introduced in Smash Bros, I started to headcanon that he was bigender, both a boy and a girl. So I kinda spit this out a while ago about my thoughts on it. I hope you all enjoy, and perhaps learns something new!
Why should he have to choose between boy and girl? Why did he only have to be one or the other?
Robin was born a boy. He was born with a boy's body. He was born with broad boy shoulders and a strong jawline. He was raised being referred to as "he" or "him." And he was comfortable in his boy body.
However, there were times when Robin was not comfortable being a boy. There were some days he wanted to be called a she, and have a girls body with soft curves. Some days he wanted to have long pretty hair and a sweet round face. He thought he was going to have to make a choice- he was either a boy, or she was a girl.
But the decision was hard. There were days when he wanted to be a boy, and there were days he wanted to be a girl. He couldn't decide which one felt more right, more like who he really was. Both fit him so perfectly that he was not sure.
Then one day, he learns a new spell. One that could let him have long or short hair, or have broad boy shoulders or a girl's slender hips, or to have the strong jawline of a man or to have the soft chin of a woman. He could cast this spell anytime he wanted to, one any day. It made it possible that he could be whatever he wanted- he could be a boy, or she could be a girl.
That was when Robin made her decision. She would be both a boy, and a girl. She did not have to choose one side or the other, and that was perfectly okay.
IMPORTANT: This is just my personal headcanon. You do not have to accept it- you can headcanon Robin as whatever you please! This was something I wanted to get off my chest because of how much I love it. So please, be respectful of another person's headcanons, whether you agree with them or not!