Guest Stars Roberts Gannaway voices Roto Rhys Darby voices Roger Rogers Nathan Fillion voices Johnny Bobby Moynihan voices Chet Corey Burton voices Slappy Kurtwood Smith voices Alistair Clawbottom Danny Pudi voices Evan Christopher Swindle voices McLean Ryan McPartlin voices Bully Monster 1 Ryan McPartlin voices Mr. April Corey Burton voices C.R.E.E.P. Worker Carlos Alazraqui voices Business Monster Danny Trejo voices Terry Emily Peterson voices Fear Co. Narrator Emily Peterson voices Fancy Monster Max Mittelman voices Convention Monsters Max Mittelman voices Scared Monster Kevin Deters voices Janitor Stevie Wermers-Skelton voices Scream Can Mascot Stevie Wermers-Skelton voices Bully Monster 2 Christopher Swindle voices Bathroom Monster Christopher Swindle voices Four-Eyed Monster Cody Rigsby voices Spin-Ergy Instructor Monster