Apatow was just 5 years old when she made her acting debut alongside her older sister Maude in "Knocked Up." The comedy was a family affair, with her father, Judd Apatow, directing and Leslie Mann and Maude playing her onscreen mother and sister, respectively. The Apatow sisters went on to star as the daughters of their mother's character in "Funny People" and "This is 40," both of which were also directed by their dad. In a behind-the-scenes clip of "This is 40," Judd shared that many of the arguments Iris and Maude have on screen are inspired by real-life conversations and fights they have off screen.