Kirk was born in New York City and and raised in Wyckoff, New Jersey. He attended the University of Southern California where he graduated in 1991 with a degree in economics and political science. He then spent three years in Italy as a journalist for an Italian film-business magazine before moving back to the United States to work for the William Morris Agency in New York City and Los Angeles. He sold his first spec script called "Day in November" to Arnold Kopelson in 1995. Since then, Kirk has been fortunate enough to adapt the work of many of his writing heroes such as: Roald Dahl, Jack Kirby and Elmore Leonard, and had the great opportunity to co-write two scripts with comedy legend John Cleese. He wrote and co-directed DreamWorks Animation's "The Croods," which was nominated for the 2013 Academy Award for Best Animated Feature.