Richard Steven Horvitz was the voice of Zim during the run of Invader Zim. He was born in LA in 1966, and currently lives there. His stage and film credits are too numerous to mention. Initially, when Richard was considered for the role of Zim, Nickelodeon discouraged the choice, since he was busy voicing Daggett on The Angry Beavers, another show that was airing at the time. As such, he did not voice Zim in the Original Pilot, and Billy West took the role instead. However, when Angry Beavers got cancelled, he was able to snatch up the part. He has recently worked on the Cartoon Network series The Grim Adventures of Billy and Mandy playing Billy and Harold, and got the role of Rodney J. Squirrel in another cancelled series, Squirrel Boy. He is now the voice of several characters in the Skylanders games.
He is happily married to playwright/screenwriter Kristen Lazarian, and they have three sons (Jake; 15 years old, Cole; 13 years old, Wyatt; 11 years old) who are strongly influenced by cartoons, and are big fans of Pokemon, as well as some of their father's shows. Along with his wife, Richard wrote Keeper of the Reaper, an episode of The Grim Adventures of Billy and Mandy. He also is the voice of Alpha 4, Alpha 5, and Alpha 7 on Power Rangers.
At the recent InvaderCON, when he was asked a question about Zim wanting Gaz as his "love-pig" (based on the various things they have in common with each other like hating the world and Dib) he joked that Zim loves Tak. (the show itself, however, never confirmed this, and Jhonen Vasquez himself has denied it, so Zim's true feelings towards Tak are left to speculation). A fan also pressed him at a signing to say he loved Dib in Zim's voice, but instead hesitated, then said: "I hate Dib! I am Zim!"
More information about Richard Steven Horvitz and his work at http://www.richardhorvitz.com/home.html.