Buckle up for a deep dive into the Planet of the Apes below!
Producer Arthur P. Jacobs, known for What a Way to Go! and Doctor Dolittle, purchased the rights to the French novel, La Planète des Singes, by Pierre Boulle, before it was published.

He saw great cinematic potential in the story of three astronauts that believed they were on a planet with superior-minded, talking apes.
Jacobs hired Rod Serling, known for his mind-twisting tales on The Twilight Zone, to write the screenplay. Serling wrote approximately thirty drafts within one year. Later, Michael Wilson rewrote the script and incorporated his feelings about the blacklist era of Hollywood into it. This wouldn’t be the first time that social commentary was injected into the science fiction franchise.
Jacobs approached Charlton Heston with the idea, hopeful that having a star attached would make a studio bite.
Heston said, “I liked the idea of the talking monkeys and the different civilization. It was simply a marvelous idea for a movie.”

Despite having a star and a strong concept, studios weren’t jumping at the chance. Finally, Richard Zanuck at Fox Studios decided to test the waters. He thought the idea had potential but was worried that the monkey costumes could make the film cheesy. So he had a test done to see how the “monkeys” would look on screen. The test, which featured Edward G. Robinson and James Brolin in monkey costumes, proved that it could be done.
Originally, the ape civilization was supposed to be a very advanced society with flying contraptions. However, due to budget constraints, they reimagined the ape society as a very primitive culture that relied on horses and lived in simple structures.
Edward G. Robinson was originally supposed to play the part of Zaius. However, due to his poor health and his discomfort wearing the makeup, he passed. Maurice Evans replaced him.

The original film could have had the alternate ending where Nova would have been pregnant, suggesting hope for the future of humanity. Instead, the surprise ending with the Statue of Liberty was chosen instead.
The first film was well received by critics and the public alike, so the studio wanted a sequel to recapture the success. Rod Serling and Pierre Boulle submitted potential ideas, but these concepts were rejected since they didn’t have the shock value associated with the first ending. Paul Dehn, known for Goldfinger and The Spy Who Came in from the Cold, was finally able to crack the idea.

One of Dehn’s rejected ideas was the idea of a hybrid ape-human child. Test footage was even shot. However, the studio felt that pursuing the idea would have jeopardized the rating and been too controversial. The studio wanted a family-friendly franchise, though this would change with the later sequels which pushed the envelope on violence and theme.
Charlton Heston did not want to do a sequel, but he was talked into it when they agreed to write off his character and introduce a new hero, played by James Franciscus.
“I think they picked Jim because he was like a smaller version of Heston,” Linda Harrison, who played Nova, said. Harrison said Franciscus took the role very seriously.

Orson Welles was offered the part of Ursus, but he declined. James Gregory was cast instead.
Two sets from Hello, Dolly! were used in the mutant city in Beneath the Planet of the Apes. A biology book inspired the makeup design of the mutants. Director Ted Post thought an image from the textbook of what humans looked like without skin fit the mutant look.

Heston came up with the ending of Beneath the Planet of the Apes with the intention that it would conclude the series. However, the film once again did well, and Paul Dehn was tasked with finding a way to create another sequel.
Three more sequels followed, then a television series, and then, years later, a reboot with its sequels.