Dave Cockrum, the man responsible for turning the X-Men into a multimillion-dollar franchise, died Sunday of diabetes in Belton, South Carolina. He was 63. His wife Paty said he died in his favorite chair wearing Superman pajamas and covered in a Batman blanket.

At Marvel Comics, Cockrum and writer Len Wein were handed the X-Men. The comic had been created in 1963 as a group of young outcasts enrolled in an academy for mutants. The premise had failed to capture fans. Cockrum and Wein added their own heroes to the comic and published “Giant-Size X-Men No. 1” in 1975. Many signature characters Cockrum designed and co-created – such as Storm, Mystique, Nightcrawler and Colossus – went on to become part of the “X-Men” films. Cockrum received no movie royalties. (Source)