You can’t copyright the setting or the theme of a comic, but you can copyright a distinctive depiction which can be recognized as a rendition of a specific character. The distinctiveness is critical. “Calvin” might be rendered different ways according to the medium used, but if someone can say “look, it’s Calvin pissing on a Ford badge”, it’s an obvious copyright violation.
A non-Calvin example of character copyright: a very informative FAQ about the copyrights applicable to Superman. The character, not the overall comic. This is proven by the fact that the character of Superman is jointly owned (50/50) by the Estate of Jerry Siegel and DC Comics, but DC Comics holds copyright of all the actual comic strips that Superman appears in. Siegel and Shuster created Superman before he was published in Action Comics #1, so they had ownership (not yet being employed by DC, so Superman wasn’t a work-for-hire). Publication of Superman gave DC an interest in the character, which is why it’s 50/50 ownership. (Shuster died without heir, so no heirs to inherit his IP.)
*As a matter of record, Bill Watterson does in fact hold a character copyright on Calvin and refuses to license it. And he (and his publisher, who defends the copyright as sole licensee of the strip) have gone to court to stop infringement.
I was excited to see this, because I thought I’d get an insight into how this would work.
But your cites don’t support the claim of a *character *copyright at all. The Legal Artist interview has this quote from Watterson:
The Techdirt article is a case of plain old ordinary copyright violation of the strip, not of the Calvin character.
The Superman case is quite different and the FAQ is interesting. But it’s not a good precedent. DC actually compromised a lot because Siegel and Shuster had the support of the entire artistic community. The outcome shows how limited the rights to that character are. The only Superman they could do would be unrecognizable to today’s readers. He couldn’t even fly!
I’m also standing on my seemingly nitpicky claim that no comic *strip *character is copyrighted, emphasizing *strip *for good reason. Superman was a comic *book *character.
The OP should just register the copyright using the normal procedure. Any talk of copyrighting characters is for message boards, not the real legal world.