When John Slattery filmed his role as Howard Stark in Iron Man 2, Marvel was riding high off the success of the first Iron Man film – but still, no one knew just how huge these movies would become.

John Slattery as Howard Stark in Iron Man 2.

Five years later, Slattery is reprising his role this summer in Ant-Man . The specifics on how this will occur have yet to be revealed by Marvel, though rumors abound about some sort of flashback scene to a younger Hank Pym.During a recent interview for Mad Men’s final episodes (more on that soon!), I asked Slattery what it was like to return to Marvel now that they’d become this huge and he said, “It’s crazy, yeah. It’s the biggest set I’ve ever seen, I think, or I’ve ever been on certainly. It’s just a gigantic room and there’s numbers and girders and you think, is that what green screen looks like? And things change so fast. The way you did special effects last year can be completed outmoded in three months when they figure out some other way of generating some image. But yeah it certainly has become like it’s an industry. Marvel is just this unbelievable force now.”Of course, an interesting aspect of the Marvel Cinematic Universe is that in the time since Slattery played Howard, Dominic Cooper has played a younger version of the character several times, including in Captain America and Agent Carter.I asked Slattery if Cooper’s performance influenced him at all and he replied, “No, I haven’t watched any of it. It took me two years to watch my own [Iron Man 2]. Well no, that’s not true. I’ve seen scenes and I’ve seen him in other things and he’s terrific. I’ve never met him and I’m not a very knowledgeable fan. I’m sure people have, 'How dare he play this when Dominic…?!' I don’t really get into that so much. My participation hasn’t been that involved. I was there for a day and whenever we did Iron Man 2, it was not that much more involved this time.”Ant-Man opens July 17th, 2015.