Rosearik Rikki Allen Simons (born September 8, 1970) is an American voice actor, writer, cartoonist, and animator. He is best known as the voice of GIR in the Nickelodeon animated series, Invader Zim. Simons has also written a number of novels and comic series, often working with his wife, Tavisha Wolfgarth-Simons.
Source: Wikipedia