Richard Steven Horvitz (born July 29, 1966), sometimes credited as Richard Wood, is an American actor and voice actor. In the world of animation, he has voiced mentally unstable and neurotic characters. He is known for his work as the voice of the original Alpha 5 in Mighty Morphin Power Rangers, Power Rangers Zeo, and Power Rangers Turbo, Razputin "Raz" Aquato in Psychonauts, Kaos in the Skylanders franchise, Billy and his father Harold in The Grim Adventures of Billy & Mandy, Grey Matter in Ben 10, Daggett in The Angry Beavers, Bumble in Kinectimals, the title character in Invader Zim, Mouth in Kick Buttowski, Orthopox in the Destroy All Humans! series, the Zoni in the Ratchet & Clank series, the Space Weaver in Broken Age and Lugosi in Bunnicula.