Littleman (2006) on Netflix

After leaving the prison, the dwarf criminal Calvin Sims joins to his moron brother Percy to steal an expensive huge diamond in a jewelry for the mobster Walken. They are chased by the police, and Calvin hides the stone in the purse of the executive Vanessa Edwards, whose husband Darryl Edwards wants to have a baby. Percy convinces Calvin to dress like a baby and be left in front of the Edwards's house to get inside the house and retrieve the diamond. Darryl and Vanessa keep Calvin for the weekend and decide to adopt him, while Walken threatens Darryl to get the stone back.