The 2008 comedy Step Brothers is a commendable film about fully grown adults who haven't managed to flee their parents' home. Commendable not in the sense that it won many awards, of course, but entertaining enough in that it allowed Will Ferrell another vehicle in which to crack puerile yet amusing gags. Mama's Boy is based on the same premise, but is less praiseworthy. Hopes are initially raised because the cast is so promising. It stars Jon Heder (Napoleon Dynamite) as the 29-year old Jeffrey, who pulls off disdain like nobody else with a mere roll of his eyes. Along with him comes Diane Keaton as his slavish mother, Jan; Jeff Daniels as Bert, her new boyfriend; and the charming Anna Faris as Jeffrey's quirky new love interest, Nora. The oddball pair bond over a mutual love of The Smiths, with whom the score is stuffed. That is one of the film's stronger points - along with a couple of droll moments that might jerk you into laughter. Keaton, amazingly, is one of the film's least strong points. Weaker than water, she is, because she hams things up too much. Remember her role in Father of the Bride and its sequel? There you go. There's a clue to the film's sophistication in its distribution history. Warner Bros opened the film in a few cinemas in America in 2007 before dispatching it to DVD. It's been trickling out internationally ever since. It was like a bad smell that the studio wanted to discretely dispel. Problem is, it still stinks.