FX's Legion is full of classic comic book ideas explored in new ways. Psychics, body-swappers, and mind-readers are nothing new to the world of comic books, but two characters on Legion seem to bring a brand-new idea to the world of comics. There aren't many comic book characters like Cary and Kerry, the two-for-one mutant pair that serves as the brains (Cary) and the brawn (Kerry) of the Summerland team. Kerry lives inside Cary which raises a lot of questions that have no easy answer — but maybe the answers lie in similar comic book characters?
Comic books are no stranger to split personalities. Marvel's most famous green beast, The Incredible Hulk, lives inside Bruce Banner. Technically, however, Bruce Banner transforms into the Hulk, which is different from Kerry's ability to simply walk in and out of Cary's body. Kerry and Cary are two separate personalities sharing one vessel, and sometimes one personality can walk around freely and beat people up. It's unlike any other split personality in comic history, but may be connected to the comic book character with more personalities than any other — Legion, aka the comic book version of Legion's David Haller who has an incomprehensible amount of power.
While the David Haller of Legion is a hyper-powerful mutant with extreme telekinetic abilities, the David Haller of the comic books isn't just David Haller. In the comic books, David Haller goes by the name Legion and has the ability to absorb other personalities and literally become different people with different powers. At last count, Legion could house anyone from a rebellious pyrokinetic woman to a rougish adventurer with telekinesis to a giant dinosaur with a clock for a face. While these mutant aren't able to talk in and out of Legion, the similarities between Legion and Cary/Kerry may hint at where the show could be going in the future.
Cary/Kerry only features one character living within another, whereas the Legion of the comic books houses an entire apartment building with Zoo built next to it. At this point, Cary/Kerry resemble the David Haller of the comics more than the television version of David Haller, but that could all be part of the show's grand plan. The show is telling the story of how David Haller becomes Legion and Cary/Kerry could be a major stepping stone in that direction. If David gets Cary's ability to house other mutants and personalities, David could become a literal one-man army.
While Cary and Kerry's mutation has no precedent in comics, it is oddly close to the defining powers of Legion. All of the powers featured on Legion have to do with the mind — be it Syd's ability to exchange minds, Ptomoney's ability to read them, or David's ability to control the physical world with his mind. Cary and Kerry share a mind — as evidenced by their choreographed dance sequence in two separate locations — but what happens if somehow these powers get mixed up and David gains the ability to house other mutants and use their powers? Perhaps Cary and Kerry are the key to David Haller becoming Legion.