Tim Holt
Lt. Cmdr. John 'Twill' Twillinger
Audrey Dalton
Gail MacKenzie
Hans Conried
Dr. Jess Rogers
Barbara Darrow
Jody Simms
Max Showalter
Dr. Tad Johns
Harlan Warde
Lt. Robert 'Clem' Clemens
Gordon Jones
Sheriff Josh Peters
Mimi Gibson
Sandy MacKenzie
Marjorie Stapp
Connie Blake
Jody McCrea
Seaman Fred Johnson
Wallace Earl
Sally
Dennis McCarthy
George Blake (lab assistant)
Sarah Selby
Mrs. Simms
Milton Parsons
Lewis Clark Dobbs
Charles Tannen
Seaman Wyatt (Radioman)
Robert Benevides
Seaman Morty Beatty
John Carlyle
Monster Victim
John Close
Deputy Larry
William Forrest
Admiral Greenhouse
Gil Frye
Deputy Scotty
Joseph Hamilton
Other Lock Watchman
Charles Herbert
Boy with Morty's Cap
Byron Kane
Coroner Nate Brown
Ralph Littlefield
Gatekeeper
David McMahon
Patterson
Ralph Moody
Watchman at Lock 57
William Swan
Seaman Howard Sanders
Hal Taggart
Davis - Resort Owner
Mack Williams
Captain Masters
Dan Gachman
Deputy Brewer
Michael Dugan
Clarke