The Stroller Strategy(2012)

Overview:

When Thomas Platz is suddenly made the guardian of a baby - then pretends to be its real father in order to win back Marie, the girlfriend who dumped him a year before. Stuck between staying a man-child forever, and proving he is ready to take the next steps of marriage and family with the love of his life, Thomas goes on an unexpectedly hilarious adventure getting the girl of his dreams to believe he has changed.