1. Electric Superman
People hate Electric Superman.
People REALLY hate Electric Superman.
Which is why those people are going to be mad right now because I LOVE Electric Superman very much.
During a period in the late nineties, Superman went through a mysterious change. Instead of his regular powers, he developed electricity and energy based powers so intense that it required him to don a containment suit. Superman had to figure out his new powers and do his job effectively without the strength and invincibility he'd gotten used to.
Writers are always complaining that "Superman is too powerful" and, while I disagree, this is the solution to that problem. The story goes to show that it isn't the powers that make Superman who he is, it's the man underneath. It also places the character in a unique position, with Clark put in a state where he actually has to figure things out on his own. Also, halfway through, Superman splits into TWO different people, Superman Red and Superman Blue and I love it maybe even more than I did before. Color coded lightning based Supermen might be the best description of why I read comic books that I ever could have typed out. It's just so fantastic.
And there ya go, ladies and gents, my list of all the different weird changes to famous comic book characters. And I didn't even mention that time Spider-Man turned into a literal spider-person.
Oh, yeah. That happened.

