Ms. Marvel ended with the amazing twist that Kamala Khan is a mutant. This departs significantly from Kamala’s comic book origins, but it’s not unusual for Marvel Comics to retcon major characters into mutants. This plot twist occurs often enough to be routine and happened to several major Marvel characters, including Wolverine.
Many X-Men characters began in the comics as non-mutants like Betsy Braddock and Moira MacTaggert, only to be revealed later to be mutants. These evolutions in their story resulted in major ramifications for the Marvel Universe, just as Kamala’s live-action origin implies big things for the MCU.
Namor The Sub-Mariner

Comic book fans know Namor the Sub-Mariner counts among the oldest characters in the Marvel Universe, predating Marvel Comics itself by two decades. From his first appearance in 1939, Namor possessed superhuman powers, but these were associated with his Atlantean physiology. That changed in Fantastic Four Annual #1, when he was revealed to be a mutant.
Namor does benefit from his hybrid human and Atlantean heritage, but his mutant abilities provide him the unique ability to fly. The X-Men attempted to recruit him in X-Men #6, and efforts to align him and Atlantis with Krakoa in modern comics proved equally unsuccessful.
Moira MacTaggert

Moira MacTaggert Some comic book fans saw key X-Men comic twists coming. No one likely saw Moira MacTaggert becoming a mutant coming. This massive twist in 2019’s House of X comics books transformed Moira from a longtime supporting character into a major figure in mutant history who resurrects each time she dies with all her memories intact.Moira’s many divergent lives led her to engineer a mutant utopia on Krakoa in recent comics but it’s since been revealed that she seeks to destroy mutants long-term for the benefit of humanity
Abigail Brand

Abigail Brand plays an important role in modern comics as the head of S.W.O.R.D. (Sentient World Observation and Response Department), tasked with defending Earth from extraterrestrial threats. She first appears in Astonishing X-Men #3, but it’s not until later that the comics reveal she is herself a mutant.
Brand generates energy from her hands, but the full scope of her powers remains a mystery. She also possesses an extraordinary ability to understand and speak alien languages, which benefits her enormously in her work and likely does when she inevitably appears in the MCU.
Psylocke

Like many characters in Marvel Comics, Psylocke evolved considerably from her original appearance. In fact, she first appeared in Captain Britain #8, a Marvel U.K. comic outside mainstream Marvel continuity, in 1976. She later appeared in American comics but wasn’t revealed to be a mutant until New Mutants Annual #2.
Her abilities and backstory evolved considerably over the years. The comics depict her as a non-mutant early on, but this changes as she becomes a key X-Men member in the 1980s and beyond.
Ultimate Iron Man

Iron Man possesses no superhuman powers in Earth-616 comics, but his Ultimate Comics variant differs. The Earth-1610 Iron Man requires his advanced armor because he was born with a genetic mutation that resulted from an accident while his mother was pregnant with him. This transformed his entire body into one giant brain.
This mutation required extraordinary protection for his highly-sensitive body, leading his father to design and develop what would eventually become the Iron Man armor.
Sabretooth

Sabretooth first appeared in Iron Fist #14 as a villain with no mutant connections. Initially, he displayed no powers at all and relied only on his super-sharp claws. His mutant status emerged thanks to his increasing connections to Wolverine, ultimately leading to Sabretooth ranking among Wolverine’s deadliest villains in the comics.
The two shared seemingly close familial connections in the comics that ultimately never developed into anything concrete, though in the movies they were shown to be related.
Madame Web

Comic book fans know Madame Web factors as a key Spider-Man ally, going back to her debut in The Amazing Spider-Man #210 in 1980. The comics initially introduce her as a clairvoyant, but in later interactions with Black Tom Cassidy and the Juggernaut, she is revealed to be a mutant with precognitive abilities.
Those precognitive abilities likely play a major role in her upcoming solo Sony Marvel Universe movie, but given the movie rights for mutants belong to Marvel Studios, the Sony Madame Web won’t be a mutant.
Madelyne Pryor

Madelyne Pryor ranks among the most evil, and most tragic, X-Men villains. She first appears in Uncanny X-Men #168 as Cyclops’ new wife and seems utterly ordinary, outside of her disconcerting physical resemblance to Jean Grey. A major twist years later established her as Jean’s clone, and Madelyne possessed all her telepathic and telekinetic abilities.
Mr. Sinister manipulated Madelyne into becoming the Goblin Queen and she attempted to destroy the world. She ultimately died, though she exists through other clones with the same powers.
Toro

Toro likely ranks among forgotten Marvel Comics characters in many fans’ minds, though he plays a significant role in Marvel history. Toro, the original Human Torch’s sidekick in the Golden Age of Comics, first appearing in Human Torch Comics #2 back in 1940. Avengers/Invaders #1 brought him into mainstream Marvel continuity and established him as a mutant.
This differs from his Golden Age origin, where he displayed a natural immunity to fire. The Human Torch discovers him at a circus, and his own unique flame-based powers activate Toro’s latent abilities.
Wolverine

Wolverine became synonymous with the X-Men as their mutual popularity grew. Wolverine first appeared in The Incredible Hulk #181, but he wasn’t a mutant at first. Co-creator Roy Thomas stated he hadn’t ‘thought that far ahead’ when he developed Wolverine alongside Len Wein and John Romita Sr and it was only when building out the roster for Giant Size X-Men #1 that Logan’s story developed.
Wolverine’s character evolved considerably during his early adventures with the X-Men. His powers and mysterious origins continued to change over time, including the fact his adamantium claws were part of his body and not his gloves, as was the case originally.