Don Terry
Larry Kent
Gwen Gaze
Toni Morrell
Walter Miller
Carter 'The Shark' Collins
George Rosener
Capt. Samuel Cuttle
Grant Withers
Roderick Gridley
Hobart Bosworth
Dr. X
Sandra Karina
Nurse Zanya
P.J. Kelly
Prof. Gault
Yakima Canutt
Dreer (Mole-Men Leader)
William Farnum
George Brennan Westmore (Editor)
Joe Caits
Saltwater Jerry [Chs.1,4-7,13-15]
Colin Campbell
Hawkins (the Butler) [Chs. 1-3]
Dave O'Brien
Det. Jameson [Chs. 4-7]
William Royle
Paul Thorndyke [Ch.1]
Warner Richmond
Capt. Tom Stanton, alias Capt. Tom Faxton [Ch.1]