Protecting your characters

You most likely want to trademark your superhero. A copyright protects a work. The trademark protects the image and the name. If your superhero is unique and has something to distinguish him from competitors, you can file for a trademark with the USPTO.

Look here.

What exactly does that entail? What is the process what protections would it bring and how far reaching are they? (Could someone simply change my superhero's cape from red to green to circumvent the trademark?)

Well, for one, registering a trademark with the government is not a requirement to use the TM or SM symbol. Anytime you are claiming rights, you can use the TM or SM (service mark). The restricted symbol, (r) is to be used only after a mark is registered (not pending). Take the Raisin Bran sun logo, "Sunny". Next to him is a tiny TM, which means the image is not registered as a trademark, but you still can't copy that image.

As far as circumventing the trademark, it's pretty obvious if someone is ripping you off. There are certain situations in which it's okay, like parody, but typically if someone takes your image and alters it only slightly, you can take action. This isn't the same as someone stealing your idea. If someone comes up with a superhero movie that is remarkably similar to yours, you're probably shit out of luck. If you have a specific image for your hero, like superman or spiderman, and someone tries to copy it or rip it off, then you've got a case.