David Wozniak (Vince Vaughn) is a hapless deliveryman for his family's butcher shop, pursued by thugs to whom he owes $80,000. His girlfriend Emma, an NYPD officer (Cobie Smulders) is pregnant with his child. One day, David returns from work to find a lawyer representing a sperm bank (where he gave 693 donations and earned a sum of $24,255 during his student years) who tells him that the clinic gave his samples to women in the clinic and that he has fathered 533 children. Of those, 142 have joined a class action lawsuit to force the fertility clinic to reveal the identity of "Starbuck," the alias he had used.
David's friend and lawyer Brett (Chris Pratt) represents him as he tries to keep the records sealed. He provides David with profiles of each party to the lawsuit; David searches for them, finding moments for random acts of kindness. David considers identifying himself but, after the thugs assault his father, he agrees with his lawyer to counter-sue the sperm bank for punitive damages. He wins the lawsuit, receives $200,000, and keeps his identity a secret.
David has regrets and thinks about revealing his identity. However, if he chooses to do so, he would lose the $200,000 that he won in the countersuit. He reveals to his father that he is Starbuck. His father decides to pay off David's debt. David finally reveals his identity on Facebook. He goes to Emma's house and finds that she is going into premature labor. At the hospital, his baby is born, he proposes to Emma, and many of the children show up to see him.
