Though Marvel previously featured a "Hercules" in the pages of the Avengers, it wasn't until Stan Lee asked Jack Kirby to create a character 'worthy' to challenge Thor. Incorporating Greek gods seemed natural...and why not Hercules, the Prince of Power!
As legend have it, Kirby being friends with 1960's actor
Steve Reeves, who played the character in movies, asked could he use his likeness as the model for the character in Marvel...and the rest is history!
JOURNEY INTO MYSTERY ANNUAL#1 1965
•first appearance Hercules
•first appearance Zeus
STAN LEE• JACK KIRBY• VINCE COLLETTA