Self (archive footage)
Leland McKenzie
Cogliostro
Cogliostro
Henry Sears
Nicholas Cogliostro (voice) (18 episodes)
Riley Hallihan
Henry L. Stimson
J. Edgar Hoover
J. Edgar Hoover
Dr. Bartholomew (voice) (2 episodes)
Barbwire Salesman
President Harry S. Truman
Leland McKenzie
Arthur Cambridge
Cromwell
Warden James Johnston
Gen. Dwight D. Eisenhower
Leland McKenzie
Leland McKenzie (171 episodes)
Harvey Koster
Dr. Nielsen
Coy LaHood
Abe
Louis B. Mayer
Hunter Burgess
Dr. Copper
Dr. Morton Freeman
Judge Russell R. Leggett
Edwin Stanton
Jack Warner
Dr. Robert Allenby
Secretary of Defense
Gen. Dwight D. Eisenhower
Trevor Isley
Dr. Brennerman
Aslaksen
Max Duval (1 episode)
Peter Bailey
President Ulysses S. Grant
Dr. Kipness (1 episode)
Leonard Driscoll (1 episode)
Leonard Driscoll
Lehman
Claude Estee
David Davis (2 episodes)
Master Bryant
Dr. John Ellis
Russ DeKuyper (1 episode)
Dr. Welbeck
Spengler
Barnes
Jerry Arnst
Motel Receptionist
Mr. Westfall (1 episode)
Accountant (uncredited)