Michael Cera

as Gunther

Jack A. O'Connell

as Mr. Hartman

Charles Grodin

as Father

Kelis

as Herself

Brandon Reilly

as Dougie

Curtiss Cook

as Conrad

Charlotte Booker

as Mrs. Hartman

Andy Prosky

as Dr. Schwartz

Christina Sajous

as Backup Singer

Deonna Bouyue

as Backup Singer

Heems

as Recording Engineer

Andrew Levine

as Adler

Adam Levite

as Man in Recording Studio

Caroline Capers Powers

as Dr. Schwartz's Date