Coproducer Owen Wilson is the title jerk-off, the best man at the wedding of a couple played by Matt Dillon and Kate Hudson. After losing his job and home, he winds up staying with the newlyweds, the houseguest from hell; meanwhile the husband is already buckling under the strain of working for his scornful father-in-law (Michael Douglas). The trailer suggested a Farrelly brothers-type gross-out complete with overflowing toilets, but working with a shapeless script, directors Anthony and Joe Russo (Welcome to Collinwood) can’t figure out what they’re making. They lunge in several directions, but fail to get around the central problem: most of their actors have little flair for comedy. I felt a twinge of envy for those in the preview audience who raced for the exit before the movie was over. They at least knew when to quit. PG-13, 108 min.