1) Ant-Headed Superman
Technically, this one isn’t a separate character, but it is a wonderful example of the madness of the Silver Age of Comics. In one issue of Action Comics in 1963, Superman briefly transformed into… Ant-Headed Superman.
After being exposed to some Red Kryptonite (which has effected the hero in various hilarious ways over the years – see also: Rainbow-Faced Superman), Supes grows an ant-like head – which handily allows him to control the horde of giant ants that are invading Earth at the time. Even more bizarre, the issue ends with Superman warning us that nuclear weapons could leave us all with ant-heads. So, you know, be warned, guys.
Maybe if a future Superman movie wanted to go down a horror movie The Fly-type route it could happen, but we’re going to go out on a limb and say that you’ll sadly never be able to watch the adventures of Ant-Headed Superman in your local theatre. One ant-related superhero is probably enough.