Max Records as Max

Catherine Keener as Mom

James Gandolfini as Carol (voice)

Lauren Ambrose as KW (voice)

Catherine O'Hara as Judith (voice)

Forest Whitaker as Ira (voice)

Chris Cooper as Douglas (voice)

Paul Dano as Alexander (voice)

Spike Jonze as Bob (voice) / Terry (voice)

Pepita Emmerichs as Claire

Mark Ruffalo as The Boyfriend

Max Pfeifer as Claire's Friend

Madeleine Greaves as Claire's Friend

Joshua Jay as Claire's Friend

Ryan Corr as Claire's Friend

Steve Mouzakis as Teacher

Michael Berry Jr. as The Bull (voice)

Vincent Crowley as Carol Suit Performer

Sonny Gerasimowicz as Alexander Suit Performer

Nick Farnell as Judith Suit Performer

Sam Longley as Ira Suit Performer

Angus Sampson as The Bull Suit Performer

Mark McCracken as The Bull Additional Suit Performer

John Leary as Douglas Suit Performer

Alice Parkinson as KW Suit Performer

Garon Michael as KW Additional Suit Performer

James Epinfaniou as Additional Max Performer

Joshua Evans as Additional Max Performer

Tess Grimshaw Lloyd as Additional Max Performer

Lucas Haynes as Additional Max Performer

Nathan Veal as Additional Max Performer

Kalia Prescott as Max's Classmate (uncredited)