Ben Feldman says he was shooting a scene as Michael Ginsberg, the newest copywriter at ad agency Sterling Cooper Draper Pryce, for the fifth season of AMC’s “Mad Men” when his co-star Aaron Staton (Ken Cosgrove) pointed out that creator and executive producer Matthew Weiner has a knack for casting actors in roles that match their real-life personalities. “I sat there thinking, ‘Well that’s great for Matt, but I’m playing this lunatic, socially awkward weirdo. What does that say about me?,’ ” Feldman asks with a laugh. I talked with the actor about his role and what goes on behind the scenes at “Mad Men.”