Mama's Boy (2007)

Eccentric Jeffrey Mannus is 29 years old and still lives at home with his mom, Jan. He sees no reason to alter this arrangement, but his perfect world is upended when Jan meets Mert, a motivational speaker. Mert successfully woos Jan and moves in on Jeffrey's territory, something Jeffrey will not tolerate. Jeffrey enlists the aid of an unlikely ally, an aspiring singer-songwriter, Nora, with an anti-establishment penchant and a soft spot for him. As the war between Mert and Jeffrey escalates, something unprecedented happens -- slowly, to both his own surprise and horror, Jeffrey discovers his inner adult.