Although a popular character in his own right, Deadpool is often perceived as an extension of the world of the X-Men due to his regular association with them, be it as a help or hindrance. However, despite his mutant-like abilities, he isn’t one, and is of the opinion that the movies are responsible for the erroneous perception that many people have.
In Deadpool #6, Wade goes off on one about not being allowed onto Krakoa, a sentient island established as a paradise for mutants, access to which is restricted via portals through which only mutants can travel. During his rant he states that due to the movies most people believe he’s a mutant and thus counts as one since “if enough people believe it then it’s basically true” and so should be allowed through the portal “on like… a technicality.”
In the first Deadpool movie, Ajax states that the purpose of the torture process was to awaken latent mutant genes possessed and unlock the potential superpowers brought with them, which in Wade’s case consisted of greatly enhanced speed, strength, agility and reflexes, and regeneration that renders him effectively unkillable. This led to the belief that Wade is himself classed as a mutant, but even in this context that’s not technically correct.
In Marvel Comics, a mutant is someone born with superpowers derived from the X-gene, typically members of the X-Men and their adversaries, whereas a mutate is someone who attains abilities via the application of external forces, such as being exposed to gamma radiation, soaked in cosmic rays, bitten by a radioactive spider, blinded by toxic waste, or enrolled as part of a clandestine government project where they’re treated with a serum derived from Wolverine’s blood designed to turn them into living weapons. Hypothetically speaking.
Mutant or mutate, Deadpool is still one of the most entertaining comic characters around – and the inspiration for some of the world’s most annoying cosplayers – and a fourth wall-breaking tirade about how fans perceive him as the result of a more widely disseminated version of himself is exactly the kind of nonsense that makes him so popular.