Nathan Fillion is a Canadian-American actor and voice actor best known for the lead roles of Captain Malcolm "Mal" Reynolds in the Fox series Firefly and its feature film continuation, Serenity, as well as Richard Castle on the ABC series Castle and John Nolan on The Rookie.Fillion has acted in traditionally distributed films like Slither and Trucker, Internet-distributed films like Dr. Horrible's Sing-Along Blog, television soap operas, sitcoms and theater. His voice is also featured in video games, such as the Bungie titles Halo 3, Halo 3: ODST, Halo: Reach, Destiny and Destiny 2, along with the 343 Industries video game Halo 5: Guardians.