- Lon Chaney Jr. - Lenny
- Jerry Colonna - Dr. Mann
- Patrice Wymore - Madame Quagmeyer
- Richard Kiel - Monster
- Peter Brocco - Mr. Swezey
- Eldon Quick - Rob Roy Fingerhead
- Byron Foulger - Groot
- Henry Corden - Babbit
- Jesslyn Fax - Mrs. Purdy
- John Hoyt - Mendoza
- Kerry MacLane - Jonathan
- Foster Brooks - Conventioneer
- Joseph Mell - Harry
- Joe Higgins - Masseur
- Monte Landis - Oraculo
- Monte Landis - Zeckenbush
- Dave Barry - Inspector Blount
- David Draper - Bulk
- Jack Goode - The Sot Lance Kibee
- Valerie Kairys - Toby Willis
- Larry Gelman - Stage Manager
- Larry Gelman - Director
- Nancy Walters - Assistant #1
- Rose Marie - The Big Man, Bessie Kowalski
- Rose Marie - Milly
- Jimmy Murphy - Tony Ferano
- Norbert Schiller - Prof. Milo Schnitzler
- Highland Dale - Jeremy (Horse) (uncredited)
- Oliver McGowan - J.J. Pontoon
- Len Lesser - George
- Len Lesser - Red
- Mel Blanc - Monkeemobile engine (voice) (archive sound) (uncredited)
- Jacqueline deWit - Kate
- Rex Holman - Sneak
- Diana Chesney - Mrs. Weefers
- Sherry Alberoni - Leslie Vandenberg
- Arch Johnson - Gen. Harley Vandenberg
- Lynne Marta - Party Guest Who's Swept off Her Feet (uncredited)
- Jack Donner - Director
- Milton Frome - Manny Spink
- Milton Frome - Latham
- Thomas Bellin - Arnold
- Carl Ballantine - Hubbell Bensen
- Nick Dimitri - Stagehand (uncredited)
- Nick Dimitri - Superman (uncredited)
- Susan Howard - Bride
- Buddy Lewis - Watchman
- Joseph V. Perry - Vernon
- Robert F. Lyons - Smasher
- George Cisar - Reporter #1
- Ray Ballard - Messenger
- Arthur Tovey - Old Man (uncredited)
- Jon C. Andersen
- Elias Davis
- David Pollock
- Ward Sylvester
- Michael Burns
- Bob Rafelson
Lon Chaney Jr. interpreta a Lenny en la serie.
Davy Jones hace el papel de Davy.
Micky Dolenz hace el papel de Micky.
Michael Nesmith interpreta a Mike en la serie.
Peter Tork interpreta a Peter en la serie.
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