The book is notable for having added names and background details on many of the minor characters who featured on-screen or in the shooting script, or even adding new characters to the story. Among them:
- Major General Raymond Hamilton, USAF divisional commander of 'SAC' (Strategic Air Command), was called upon to decide if the strange unidentified vehicle was the opening shot in a nuclear war. This character is also referenced in the 2011 novel Conspiracy of the Planet of the Apes.
- Surgeon Lt. Commander Gordon Ashmead, subordinate to 'Snapper' Jardin. He was onboard the recovery ship that picked up the 'ape-o-nauts'.
- Bill Cummings, reporter sent to interview Cornelius and Zira for Men's Hunting And Outdoors.
- Jeanna Robbins, reporter for Fur and Feather magazine. She thought Zira was "..an absolute pet".
- Joe Simpson, reporter sent by Ebony magazine to interview the apes from the future, asked some difficult questions.
- Doctor Raymond Wilson, a naturalist specializing in the great apes, and a later member of the Inquiry Commission.
- Sergeant Miessner, an aide to Hasslein, and the actual killer of Cornelius.
A German translation of Pournelle's novel by Walter Brumm was published in 1976 by 'Pabel Terra TB'.