Justin Long. Justin Jacob Long performed the voice of Humphrey in Alpha and Omega. He appears in the "Making of Alpha and Omega" feature. He is best known voicing as Alvin Seville from live action films, Alvin and the Chipmunks and its sequels. Retrieved from "https://alphaandomegafilm.fandom.com/wiki/Justin_Long?oldid=26950" Categories: Real people Alpha and Omega Actors Voice Actors Real Life Community content is available under CC-BY-SA unless otherwise noted.