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