The X-Men have been staples of the Marvel Comics line since they first appeared in 1963. Hundreds of mutants have come and gone with events and crossover arcs that spotlight all of Marvel's not-so-merry mutants. There have been movies, cartoons, and countless prose books that feature their struggle to protect a world that hates and fears them.
Source:https://www.cbr.com/xmen-secrets-hardcore-fan-trivia/