Planet of the Apes went from book to screen during one sweltering Arizona summer in 1967, following a few years of rejected scripts and studios refusing to greenlight the project. Some might say the film fought a battle of its own. We say it was a fight well worth it.

The original 1968 Planet of the Apes and its sequels topped box offices in each of their release years, making the series not only one of the most head-turning sci-fi epics, but one of the most successful as well.

Modern day Planet of the Apes fans, here are ten things you should know about the original classics behind it all:

  1. Producer Arthur P. Jacobs purchased the movie rights to Pierre Boulle’s book, La Planète des Singes, before the book had even been published.

  2. The first film had a cast of over 200 apes, requiring an 80-person makeup and wardrobe crew. In fact, the demand for this personnel was so significant that competing films in production at the time were delayed due to a shortage in professionals.

  3. The actors playing chimpanzees, orangutans, and gorillas were not required to stay separated during filming--but they did anyway. The actors playing the same species of apes tended to stay together on set.

  4. John Chambers was the man behind the revolutionary makeup effects of the original Apes series. During World War II, he’d used similar techniques to give veterans with disfiguring injuries a normal appearance. For his innovations, the Academy of Motion Picture Arts and Sciences gave Chambers an honorary award for make-up, even though there was no official Oscar category for make-up until 1981.

  5. Speaking of WWII, the rifles used by the apes in the films were actual remodeled M1 semi-automatic carbines used by American forces during the war.

  6. Following the success of the first film, Pierre Boulle wrote a screenplay for a sequel entitled Planet of Men, featuring a human uprising that eventually reverted the apes back to their animalistic states.

  7. When the second film was just as much of a hit as the first, producer Arthur P. Jacobs sent a telegram to his writer, stating simply: “Apes exist. Sequel required.” Short, sweet, and to the point!

  8. The Arizona heat during the filming of Planet of the Apes was so insufferable for the actors and crew (especially those in heavy makeup), that each of the four sequels were filmed in the winter.

  9. Four out of five films in the original Planet of the Apes series were rated G. Film number four, Conquest of the Planet of the Apes, was rated PG because it was much more violent. There are 59 deaths in this film.

  10. The final film in the original series, Battle for the Planet of the Apes, is allegedly the movie that inspired operation “Argo” during the Iran Hostage crisis from 1979 to 1981, in which Tony Mendez helped hostages escape from Iran under the guise of a producer and his film crew. “Argo” is the title of the fake script used during the operation, which was chosen by Apes makeup artist John Chambers.