- Otto Von Werner - prospective defector killed by Milton Conrad [Portrayed by Tol Avery , Episode #38: "Hoo Done It"].
- Otto Hurrah - Hollywood producer-director and mastermind behind the theft of Formula 6076767 aka "DryUp" [Portrayed by John Myhers, Episodes #58 & 60: "A Man Called Smart, Parts 1 & 3"].
- Otto of Oberfurstengogel - henchman to Prince Basil of Caronia [Portrayed by Richard Angarola, Episode #74: "The King Lives?"].
- Otto - henchman to Miss Magruder [Portrayed by Max Kleven, Episode #81: "Operation Ridiculous"].
- Otto - henchman to Rupert of Rathskeller [Portrayed by Pat McCormick (uncredited), Episode #107: "To Sire, With Love, Part 2"].
- Otto Greer - head of Greer Industries from where secret government information is disappearing [Portrayed by Barney Phillips, Episode #110: "Greer Window"].
- Otto Cronin - liaison to scientist Dr. Mathew Rath [Portrayed by Bob Carroll, Episode #122: "The Apes of Rath"].