Guest Stars Christopher Swindle voices Phlegm Alanna Ubach voices Carla Dee Bradley Baker voices Banana Bread Nathan Fillion voices Johnny Ali Wong voices Jill Jenifer Lewis voices Grandma Tuskmon Joe Lo Truglio voices Jack Alanna Ubach voices Maria Alan S. Kim voices Ben Aubrey Plaza voices Claire Julia Butters voices Lorelai Carlos Alazraqui voices Josh Rivera Sander Argabrite voices J.J. Alfred Molina voices Professor Knight Romi Dames voices Lanky Christopher Swindle voices Rudy the Service Monster Romi Dames voices Student Monsters Carlos Alazraqui voices Jebediah Nohely Quiroz voices MU Student Natalie Lashkari voices Little Girl Monster Nohely Quiroz voices MNN Receptionist Max Mittelman voices Student Monsters Max Mittelman voices Large Monster Max Mittelman voices RQR Bro Co Starring Christopher Swindle voices Additional Monsters