Michael Sheen as Dr. Slavkin O'Hara

Toni Collette as Patricia Herman

Jason Spevack as Henry James Herman

Samantha Weinstein as Audrey O'Hara

Melyssa Ade as Kindergarten Teacher

Oprah Winfrey as Oprah

Frank Moore as Stan Herman

Paul Braunstein as Dr. Gunther Flowers

Hannah Brigden as Young Patricia Herman

Sarah Orenstein as Mother Herman

Jamie Johnston as Young Billy Herman

Mark MacDonald as Tim Herman

Mickey MacDonald as Tom Herman

Cameron Kennedy as Jimmy Herman

Kate Hewlett as Alice O'Hara

Kevin Hare as Delivery Room Doctor

Austin Macdonald as Brian the Bully

Mishu Vellani as Miss Abda

Aaron Abrams as Malcom's Dad / Nurse Stewart