Oh, Shirtless Paul Rudd. You are Shirtless Paul Rudd and you’re not even the best thing in this trailer. “This Is 40″ is the sort-of sequel to “Knocked Up,” about Paul and Debbie, the sister and brother-in-law of Katharine Heigl’s character. Now they’re 40 and feeling positively ancient. But they’re still got pot brownies, a gorgeous home, two great kids, and people in their lives like Megan Fox, Chris O’Dowd, and Jason Segel. Doesn’t sound too shabby to me. By all means, Leslie Mann, take 28. I’ll hand it over for half a pot brownie and a romp in the sack with your onscreen husband.