Thanks a lot, Kang! After decades of menacing Marvel's heroes, the fictional character has caused a commotion in the real world. For those trying to keep track of film rights, the revelation that Kang the Conqueror actually resides within 20th Century Fox domain and not Marvel Studios was a real head scratcher. For those of you unaware of Marvel's byzantine film rules, we'll do our best to break down this Kang conundrum.

Unlike DC Comics, the film rights for Marvel Comics' characters are not all owned by Marvel Studios -- the film company behind the Marvel Cinematic Universe that kicked off in 2008 with "Iron Man." Prior to the formation of Marvel Studios, Marvel Comics had to sell off film rights in order to get movies made; Sony got Spider-Man, Fox gained the X-Men and Fantastic Four, Lionsgate had Punisher and Universal landed Namor. This didn't happen to the DC characters because DC Comics has been a part of Warner Bros. since the late '60s; that film studio has released all of their feature films, from the 1978's "Superman" up through to 2013's "Man of Steel" and beyond. Conversely, Marvel's characters remain separated, tied up in the deals made before the launch of their shared film universe in 2008.

RELATED: Gunn Discusses Possibility of Kang Battling the Guardians of the Galaxy

While the details of those deals between Marvel and other film studios have never been made public, fans have operated under a handful of rules when trying to figure them out -- the most logical one being that the film rights are determined by the comic book a character first appeared in. "Fantastic Four" and "X-Men" debuts are with Fox, "Spider-Man" with Sony, nearly everything else with Marvel. Kang belonging to Fox both breaks and confirms this rule -- that's why it's confusing! Kang debuted in "Avengers" #8 and is primarily an Avengers antagonist, so he should be owned by Marvel Studios but he's not. That's how he breaks the rule. But in actually, another iteration of Kang -- a villain called Rama-Tut -- debuted in the pages of "Fantastic Four" almost a year prior to that "Avengers" issue. By that logic, Rama-Tut/Kang's rights do belong with Fox even if he's primarily an Avengers bad guy. That's how he confirms the rule.

So with all that background info outta the way, wow, let's look at the characters from the past, present and future that defy this "first appearance" rule. And just to help guide you along: "Sony" in quotes refers to characters that debuted in Spider-Man comics; "Fox" refers to characters that debuted in Fantastic Four and X-Men comics; and "Marvel" refers to pretty much everyone else.

"Fox" Characters In Marvel Movies





Because of its role as the first ongoing Marvel series, a lot of characters debuted in the pages of "Fantastic Four." In the case of Galactus and Silver Surfer, that means their rights are owned by Fox. In the case of other characters -- not so much. Both the Kree and Ronan the Accuser, who we saw in "Guardians of the Galaxy" debuted in "FF" (in issues #64 and #65, respectively). The villain Klaw debuted in "Fantastic Four" #53 and played a part -- as Ulysses Klaue -- in "Age of Ultron." Additionally, the superhero Black Panther debuted in "FF" #52, and he's about to show up in "Captain America: Civil War" as well as his own feature film.

Quicksilver and Scarlet Witch were thought to be Fox characters because they debuted in "X-Men" #4 and are mutants -- or at least they were until Marvel Comics undid that fact a few months ago. Marvel admitted that the twins exist in a gray area that allowed Quicksilver to appear in both Fox's "X-Men: Days of Future Past" and "Avengers: Age of Ultron", but it's odd that Kang doesn't also exist in that gray area. The twins seem to have been grandfathered in due to their lengthy tenures as Avengers in the comics; Kang, despite being primarily an Avengers antagonist, was not afforded that same status.

"Marvel" Characters In Fox Movies





A surprising number of big deal X-Men characters debuted outside of Marvel's mutant line. Rogue debuted in "Avengers Annual" #10 and Wolverine slashed into action in "Incredible Hulk" #180. Mystique was introduced as a Ms. Marvel villain ("Ms. Marvel" #16) and Sabretooth threw down with Iron Fist ("Iron Fist" #14) long before he appeared in "Uncanny X-Men." And both bad guys from Fox's "The Wolverine" film, Viper and Silver Samurai, debuted in Marvel Universe comics -- "Captain America" #110 and "Daredevil" #111. All these guys disobey the "first appearance" rule, because they're mutants that are almost singularly tied to the X-Men.

"Sony" Characters In Other Movies





As if things weren't already confusing, Sony's recent partnership with Marvel that allows them to share Spider-Man's movie rights has potentially brought a number of characters -- we'll get to them in a moment -- into the Marvel Cinematic Universe. But one character was pegged for Marvel Studios' "Daredevil" Netflix series before Marvel and Sony reached that deal, thus defying the "first appearance" rule. Kingpin debuted in "Amazing Spider-Man" #50 and, because he eventually became one of Daredevil's biggest bads, he was included in the package Marvel sold to Fox in the early '00s. When Fox let those rights lapse, Daredevil and all of his supporting characters -- including Wilson Fisk -- went back to Marvel Studios. Kingpin is a character that, according to the "first appearance" rule, should have been owned by Sony -- but he instead passed between Fox and Marvel.

Despite their origins in "Amazing Spider-Man," both Punisher and Jigsaw ended up in Lionsgate-produced films. Thanks to more lapsed rights, though, both characters are now back at Marvel Studios. The mutant hero Siryn debuted in "Spider-Woman" #37, which could have made her a Sony character, but she appeared in cameo roles in Fox's "X2" and "X-Men: The Last Stand."

Now that we've looked at all the head scratchers that have caused us to, well, scratch our heads, let's look towards the future at characters that could cause some Kang-style confusion when/if they get called up to the feature film big leagues.

The Inhumans





Wait, I know what you're thinking -- these guys have a Marvel Studios feature film slated for release in 2019. Of course they're Marvel characters. Like the Kree and Black Panther before them, the Inhumans debuted in "Fantastic Four" but avoided getting lumped in with their film rights. But both Crystal and Medusa have been members of the FF before, and being members of both the Avengers and X-Teams allowed Quicksilver to pop up in both Fox and Marvel movies. It's likely that no A-list -- or even B-list -- Inhumans have appeared in Marvel's "Agents of S.H.I.E.L.D." because they're saving them for the film, but what if they're avoiding Medusa, Black Bolt, Lockjaw and the rest because the rights are Scarlet Witch-level murky? But that's a long shot; it's highly unlikely that Marvel would announce a movie starring characters they don't own the rights to -- but it also wouldn't be a surprise if some of them (Gorgon, Karnak, Triton?) were in Fox's hands.

Fox Characters?





Despite branching out to the wider Marvel Universe, both Agent Abigail Brand of S.W.O.R.D. and the alien race known as the Phalanx debuted in X-Men books, so it's likely they won't be showing up in the MCU. The same might be true for Alpha Flight and its members -- except the Canadian government agency that overlooks them, Department H, was mentioned in the "S.H.I.E.L.D." episode "End of the Beginning." Can Puck get namedropped in "Civil War," then?

A few more alien races are also out of the mix: James Gunn has previously mentioned that Marvel only partially owns the Skrulls and does not own the Badoon. The Badoon, despite being majorly tied to the original Guardians of the Galaxy, debuted in "Silver Surfer" #2 -- so the "first appearance" rule applies to them? If that's the case, then other characters that debuted in "Silver Surfer," like Mephisto and Captain Mar-Vell's son Genis-Vell, might also be at Fox.

But, as evidenced by Black Panther and the Kree, debuting in "Fantastic Four" isn't always synonymous with Fox. Could the Watcher, Terrax or Adam Warlock -- all characters that debuted in "FF" -- show up in a Marvel movie? And let's not forget iconic Avenger D-Man, whose debut in "The Thing" #28 could keep him from assembling alongside Iron Man and Cap, where he belongs.

Marvel Characters?





Not all mutants debut in X-Books. New Warriors member Justice debuted in "Giant-Size Defenders" #5; X-Factor ward-turned-member Layla Miller made a big debut in the "House of M" event; and New Mutants characters Karma and Boom Boom debuted in the pages of "Marvel Team-Up" and "Secret Wars II," respectively. Sabra may have never been an X-Man, but she is a mutant and got her start in "Incredible Hulk" #250. We know Marvel can't use any of them as mutants, but could they use them if they made them Chitauri-enhanced humans like the Maximoffs?

To add another layer, there are also some non-mutant X-Men characters that debuted outside of X-Men comics. Deathbird was originally a "Ms. Marvel" villain and, as a member of the alien Shi'ar, is probably tied up with Fox. But what about the other-dimensional Longshot and his supporting cast (Mojo, Spiral) or Arcade, the human assassin who uses a giant pinball machine as a weapon? None of them are traditional mutants and none of them debuted in an X-Men comic.

Then there are Captain Britain and Meggan, two non-mutant characters with close ties to the X-Men who debuted outside of the X-Line and existed for quite a while before joining Excalibur. They were also created by Alan Moore, a writer that has been openly hostile towards film adaptations of his work. And then there's Machine Man of "Nextwave," a character not at all affiliated with the X-Men but instead with the feature film "2001: A Space Odyssey"; he debuted in Marvel's continuation of the comic book adaptation of the film. So... could his rights be split between Marvel Studios and MGM?

And Then There's Namor





Namor's trajectory since his debut over 75 years ago, from Avenger to X-Man to Atlantean to mutant to solo hero to Fantastic Four antagonist, has left us unable to apply any logic or rules to where his rights might be. That's a good thing, though, because we know where they are... sorta. Namor was the lone hero left at Universal (unless that initial deal included spinoff characters like Namora and Namorita -- oh geez, does it?), but Marvel Studios President Kevin Feige has stated that they are working on getting him firmly back in the Marvel fold. It's possible that the Sub-Mariner is swimming back toward the MCU, like Punisher, Ghost Rider, Blade and Daredevil before him. That swim might take a long time, though.

After wading through all that uncertainty, let's close this out on a positive note by listing off some of the characters whose rights were previously head scratchers, but most likely aren't anymore thanks to the relatively recent partnership between Sony and Marvel. Odds are Marvel can now figure out how to work in predominantly Marvel characters that debuted in Spider-Man comics -- like Silver Sable, Sandman, Flash "Venom" Thompson, Monica Rambeau, Speedball, Norman Osborn and all the Spider-Women and Spider-Girls and Spider-Gwens --into their massive cinematic universe. Now if only Marvel could work something out with Fox, then this article could be totally obsolete.

Except for Namor.