We know The Simpsons had guest voices including Zach Galifianakis, Paul McCartney, Daniel Radcliffe and many others, but there should be other guest stars to voice new characters on the show, including Bill Hader, Amy Poehler, Scarlett Estevez, Hadley Belle Miller, Will Smith, Emily Hahn, Zelda Williams, Jeffrey Tambor, Will Ferrell, Linda Cardellini and Mark Wahlberg. Sign here if you want them to voice new characters on the cartoon animated comedy show.