| David Duchovny | Fox Mulder |
| Gillian Anderson | Dana Scully |
| Mitch Pileggi | Walter Skinner |
| Barbara Hershey | Erika Price |
| Annabeth Gish | Monica Reyes |
| Lauren Ambrose | Agent Einstein |
| Robbie Amell | Agent Miller |
| Chris Owens | Jeffrey Spender |
| Anjali Jay | Dr. Joyet |
| A.C. Peterson | Mr. Y |
| William B. Davis | Cigarette Smoking Man /
True Name Carl Gerhard Busch |
| Arghavan Jenati | Female Paramedic
(as Arggy Jenati) |
| Harry Han | Male Paramedic |
| Nia Cummins | Nurse
(as Naiah Cummins) |
| Sandy Da Costa | Alien |
| Jeremy Schuetze | Young CSM |
| Fiona Vroom | Young Cassandra |
| Jett Klyne | Young Spender |
| Alexandre Campion | Young Mr. Y |
| Erica Govier | Young Erika |
| George Bush | Self
(archive footage) (uncredited) |
| George W. Bush | Self
(archive footage) (uncredited) |
| Bill Clinton | Self
(archive footage) (uncredited) |
| Hillary Clinton | Self
(archive footage) (uncredited) |
| Mike Dopud | The Driver
(uncredited) |
| Michael Flynn | Self
(archive footage) (uncredited) |
| Shannon Hile | Mrs. Van De Kamp
(uncredited) |
| Adolf Hitler | Self
(archive footage) (uncredited) |
| Robert F. Kennedy | Self
(archive footage) (uncredited) |
| Mark Lewis Oglesby | Stanley Kubrick
(uncredited) |
| Richard Stewart Rigby | Hand Double for Mr Y
(uncredited) |
| Miles Robbins | Jackson Van De Kamp
(uncredited) |
| Anthony Scaramucci | Self
(archive footage) (uncredited) |
| Sean Spicer | Self
(archive footage) (uncredited) |
| Donald Trump | Self
(archive footage) (uncredited) |
| Melania Trump | Self
(archive footage) (uncredited) |