Arnie will call asking you drop by his office. Once there he'll tell you about a lead in an upcoming sitcom about ninjas. He can get you a copy of the script soon, but before that try to get some sitcom experience under your belt, because ninjas wear belts, right?
Note: Arnie will call you with various projects that you may choose to take on, but read carefully when accepting these. In order to complete this goal you need it to be a "Sitcom".
After you've completed a sitcom Arnie will tell you that filming Our Son the Ninja starts in 8 hours. He'll call when the script is available.