| Dan Stevens | David Haller |
| Rachel Keller | Syd Barrett |
| Aubrey Plaza | Lenny Busker |
| Bill Irwin | Cary Loudermilk |
| Jeremie Harris | Ptonomy Wallace |
| Amber Midthunder | Kerry Loudermilk |
| Katie Aselton | Amy Haller |
| Jean Smart | Dr. Melanie Bird |
| Hamish Linklater | Clark |
| David Selby | Brubaker |
| David Ferry | Dr. Kissinger |
| Ellie Araiza | Philly |
| Matt Hamilton | Ben |
| Brad Mann | Rudy |
| Quinton Boisclair | Devil with the Yellow Eyes |
| Mackenzie Gray | The Eye |
| Mike Azevedo | 'Renal Failure' Alvarez |
| Ese Atawo | Day Room Duty Nurse |
| Tobias Austen | David (Infant) |
| Noah Hegglin Houben | David (Infant) |
| Sebastian Billingsley-Rodriguez | David (Toddler) |
| Christian Convery | David (4 Years Old) |
| Luke Roessler | David Haller (6-8 Years Old) |
| Jacob Hoppenbrouwer | David (10-12 Years Old) |
| Alex Mulgrew | David (16 Years Old) |
| Paul Belsito | The Man Who Hides |
| Eugene T.S. Wong | The Man In All His Clothes |
| Eric Malapad | The Man Who Strokes His Beard |
| Gustavo Ferman | Risotto Dude |
| Stephanie Van Dyck | Skeletal Fat Lady |
| Tim Bissett | Psychiatrist |
| Sidartha Murjani | Wild Rusty Combs |
| Georgia Swinton | Woman Who Self-Argues |
| Espirito Mauricio | Woman Who Nurses |
| Kyja Sutton | Amy (8-10 Years Old) |
| Matt Afonso | Monitor Room Technician |
| Davin Tong | Cube Tech #1 |
| Jesse Reid | Cube Tech #2 |
| Simon Chin | Clockworks Orderly |
| Charles Jarman | Cube Police #1 |
| Shimon Boriskov | Jr. Prom Guy (Bloody Nose) |
| June B. Wilde | Science Teacher |
| James Wilson | School Principal |
| Maddie Phillips | Jr. Prom Date (Crying) |
| Mathias Ty Parto | Trick or Treater #1 |
| Jonathan Wu | Trick or Treater #2 |
| Belinda Sobie | Patient Dancer #1 |
| Sabine Uwibambe | Patient Dancer #2 |
| Karina Ho | Patient Dancer #3 |
| Edwin Perez | Patient Dancer #4 |
| Mandy Rushton | Patient Dancer #5 |
| Monica Gutierrez | Patient Dancer #6 |
| Stephanie Lavigne | Patient Dancer #7 |
| Jim Eliason | SWAT Team 3 |
| Kari Staten | Townsperson |