Cristin Milioti

Grace

Delaney Quinn

Freddy

Topher Grace

Ben

Keegan-Michael Key

Buddy the Unicorn (voice)

Michael Shannon

Charlie the Train (voice)

Patton Oswalt

Strappy (voice)

Clint Howard

Sergey Zhuravsky

Buddy the Unicorn

Madison Polan

Hannah

Bryson JonSteele

Derek

Seamus Flynn

Timothy

Bennie Taylor

Mailman Miles

Mark Aaron Buerkle

Therapist (Day Player)

Phuong Kubacki

Luke Speakman

Josh

Tristan Borders

Oliver

Caleb Williams

Wade

Conner Stumm

Mailman Justin

Eric Salazar

Dad

Lynette Eklund

Puppeteer

Tory Jacqui Malone

Tyler

Rachel Appelbaum

Clocky / Mr. Mailbox

Cedwan Hook

Betty Bunny Puppeteer

Jonathan Yurco

Dark Buddy

Frank Brown Jr.

Father