 Cristin MiliotiGrace | Grace |
 Delaney QuinnFreddy | Freddy |
 Topher GraceBen | Ben |
 Keegan-Michael KeyBuddy the Unicorn (voice) | Buddy the Unicorn (voice) |
 Michael ShannonWillie (voice) | Willie (voice) |
 Patton OswaltStrappy (voice) | Strappy (voice) |
 Clint HowardGeorge | George |
 Eric BauzaMr. Mailbox / Worry Well / Couchy / Trashy / Pee Flower (voice) | Mr. Mailbox / Worry Well / Couchy / Trashy / Pee Flower (voice) |
 Sergey ZhuravskyBuddy the Unicorn (suit) | Buddy the Unicorn (suit) |
 Jonathan YurcoDark Buddy (suit) | Dark Buddy (suit) |
 Devon Hawkes LudlowCharlie the Train (voice) | Charlie the Train (voice) |
 Jimmica CollinsBetty Bunny (voice) | Betty Bunny (voice) |
 Madison PolanHannah | Hannah |
 Bryson JonSteeleDerek | Derek |
 Seamus FlynnTimothy | Timothy |
 Bennie TaylorMailman Miles | Mailman Miles |
 Cedwan HooksBetty Bunny (suit) | Betty Bunny (suit) |
 Mark Aaron BuerkleTherapist (Day Player) | Therapist (Day Player) |
 Phuong KubackiNurse Nancy | Nurse Nancy |
 Luke SpeakmanJosh | Josh |
 Noah Pierre D.Jakson (uncredited) | Jakson (uncredited) |
 Tristan BordersOliver | Oliver |
 Caleb WilliamsWade | Wade |
| CConner StummMailman Justin | Mailman Justin |
 Eric SalazarGrilling Man | Grilling Man |
| LLynette EklundPuppeteer | Puppeteer |
 Tory J. MaloneTyler | Tyler |
 Brooke BloomDr. Deborah Burr | Dr. Deborah Burr |
 Rachel AppelbaumClocky / Mr. Mailbox (uncredited) | Clocky / Mr. Mailbox (uncredited) |
| FFrank Brown Jr.Father (uncredited) | Father (uncredited) |
