Our Idiot Brother floats by on the genial charms of Paul Rudd, an apparently nice guy in real life who’s playing just about the nicest, most pleasant guy in the world. That sounds like a recipe for ho-hum disaster, but Rudd happens to be ridiculously adept at selling you two bags of goods at once, imbuing that geniality with a fount of deep tangible feeling. Audiences accustomed to Judd Apatow-era Rudd might forget that he’s acted in Neil LaBute plays and films (before LaBute turned into a director-for-hire) and once played F. Scott Fitzgerald’s Nick Carraway in a Great Gatsby adaptation made for TV. The guy has dramatic chops, and he’s one of the few actors in Hollywood who can naturalistically flow them into a deceptively low-key framework. Here, Rudd stars as Ned — or Nedley, as mom calls him — a lovable, trusting hippie farmer who sells a cop some weed and winds up in jail. After his release, with nowhere to go, Ned moves in first with mom and then with his three high-strung sisters in succession.