Kevin Hart

George (voice)

Thomas Middleditch

Harold (voice)

Ed Helms

Captain Underpants / Mr. Krupp (voice)

Nick Kroll

Professor Poopypants (voice)

Jordan Peele

Melvin (voice)

Kristen Schaal

Edith (voice)

DeeDee Rescher

Ms. Ribble (voice)

Brian Posehn

Mr. Rected (voice)

David Soren

Tommy (voice)

Mel Rodriguez

Mr. Fyde (voice)

Susan Fitzker

Ms. Dayken (voice)

Lynnanne Zager

George's Mom (voice)

Tiffany Lauren Bennicke

Sad Girl (voice)

James Ryan

Mime (voice)

Leslie David Baker

Officer McPiggly (voice)