Apart from performing as a live instrumentalist, Fitzgerald has also worked as a composer and songwriter, having worked with a wide range of musicians including Dweezil Zappa and Danny Elfman, and has written songs for the movie School of Rock. He also provided string arrangements for the Alkaline Trio album Crimson and contributed guitar work to the Team America: World Police soundtrack. As of 2012, Fitzgerald is credited as a writer and composer on The Hub cable series The Aquabats! Super Show!, including a co-composing credit for the series' theme song and several onscreen appearances playing a hobo.
Outside of his music, Fitzgerald finds work as both an artist and a writer.