For Marvel in the 1960s, Hartley drew a single superhero comic: an episode of the Norse god superhero feature "Thor" in "Journey into Mystery" #90. He recalled that "superheroes weren't really my forte. I don't recall the circumstances that led me to draw that story. At that stage of the game, I was mostly doing work that I was more comfortable with, mostly teenage and humor stories." Harley dabbled in Marvel scripting on two stories: the "Iron Man" feature in "Tales of Suspense" #68 (Aug. 1965), and the last "Giant-Man" feature, in "Tales to Astonish" #69 (July 1965).