“It was just difficult to figure out where I was going to come from with Superman ,” Gunn said speaking to io9 in Los Angeles last week. “And I think that it really started with my dog in a lot of ways. The idea of putting in Krypto, I think, was the fun part for me, because that was something that we hadn’t really seen in a Superman movie.”

A new photo book, with an introduction by James Gunn, offers a behind-the-scenes look at the making of the new Superman, out this July.