Listen to A Man's Gotta Do online. A Man's Gotta Do is an English language song and is sung by Neil Patrick Harris, Felicia Day and Nathan Fillion. A Man's Gotta Do, from the album Dr. Horrible's Sing-Along Blog (Motion Picture Soundtrack), was released in the year 2008. The duration of the song is 99:01:01. Download English songs online from JioSaavn.