Brian Hiatt on how Stan Lee created the X-Men:
He had already done the radioactive-accident thing at least three times, so Lee went in another direction: “I took the cowardly way out,” he says. “I figured, hey, the easiest thing in the world: They were born that way. They were mutants!” He called the team the Mutants, until Marvel’s publisher told him kids didn’t know the word. Instead, Lee settled on the X-Men (“I figured, they have extra powers, and their leader is Professor Xavier”). Lee spent maybe a day on the proposal and another day plotting the issue; Kirby, a pulp genius World War II vet who’d chomp on his cigar while cranking out as many as five pages a day, designed all the characters as he drew the first story.
The best part of the story is that Marvel was at the point of near bankruptcy when Fox greenlit the first X-Men film. Nine years later, Disney bought the company for $4 billion — which would be considered a steal now, given just how much of Hollywood box office receipts Marvel IP now drives.