Christopher Jon Castile (born June 15, 1980) is an American professor and former actor. His well-known roles include Ted Newton in Beethoven and Beethoven's 2nd, the voice of Zachary Sellers and Nick Mulligan in Focus on the Family's Adventures in Odyssey, Mark Foster on the sitcom Step by Step, and the voice of Eugene Horowitz in Hey Arnold!.
Following the cancellation of Step by Step, Castile retired from acting and went on to earn a bachelor's and master's degree in political science from California State University, Long Beach. He currently teaches political science at Biola University in La Mirada, California, and U.S. history at Downey High School.