Suggestions by @pnutcavanaugh

Bill Farmer

as Nit Wit in Riddle School

Tom Hardy

as Viz in Riddle School

Tom Kenny

as Quiz in Riddle School

Seán William McLoughlin

as Messie in Riddle School

Markipiler-Mark Edward Fishbach

as Goat-Man in Riddle School

Bonnie Hunt

as Ms. Cophey in Riddle School

Lewis Dawkins

as Bigtoe in Riddle School

Keith David

as Diz in Riddle School