Actors in both Smallville and The X-Files
147 actors have appeared in both Smallville and The X-Files, across 435 episodes. The most-credited is William B. Davis, Mayor William 'Billy' Tate in Smallville and Cigarette-Smoking Man in The X-Files.
| Actor | In Smallville | In The X-Files | Eps | Eps |
|---|---|---|---|---|
| William B. Davis | Mayor William 'Billy' Tate | Cigarette-Smoking Man | 2 | 44 |
| Bruce Harwood | Ben Powell | John Fitzgerald Byers | 1 | 38 |
| Mitchell Kosterman | Sheriff Ethan Miller | Detective Horton, Fornier, Sheriff | 14 | 4 |
| Alessandro Juliani | Dr. Emil Hamilton | Joseph Cutler | 14 | 1 |
| Sarah Jane Redmond | Nell Potter | Karin Matthews, Young Mother | 11 | 2 |
| Mike Dopud | Security Guard George | Mr. Y's Henchman | 10 | 1 |
| Hiro Kanagawa | Principal H. James Kwan | Dr. Yonechi, Garner, Peter Tanaka | 5 | 3 |
| Malcolm Stewart | Dr. Otis Ford, Dr. Sinclair, Jim Melville | Dr. Sacks, Agent Bonnecaze, Commander Carver | 3 | 5 |
| Robert Wisden | Gabe Sullivan | Robert Patrick Modell aka Pusher | 6 | 2 |
| Sharon Taylor | Faora | Diana Eggers | 7 | 1 |
| Tom O'Brien | Roger Nixon | Corporal Frish | 5 | 2 |
| Fred Henderson | Dr. Langston | Agent Rich, Agent Thomas | 4 | 2 |
| Jerry Wasserman | Dr. Yaeger Scanlan | Dr. John Grago, Dr. Plith | 4 | 2 |
| Michael McKean | Perry White | Morris Fletcher | 2 | 4 |
| Stephen Lobo | Randall Brady | Dark-Suited Man #1 | 5 | 1 |
| William MacDonald | Walt Masterson | Agent Dan Kazanjian, Buddy Riggs, Dr. Oppenheim | 1 | 5 |
| Gillian Barber | Marianne Taylor | Penny Northern, Agent Jane Spiller, Beth Kane | 1 | 4 |
| Joe Morton | Dr. Steven Hamilton | Martin Wells | 4 | 1 |
| Colin Lawrence | Agent Stocker, Captain Nichols, Doctor | Cop #1 | 3 | 1 |
| Rob LaBelle | Dr. Fredrick Walden | Brad Wilczek | 3 | 1 |
Cast data from TVmaze, licensed CC BY-SA 4.0.