What a classic! And what an underrated work of genius.
Like all good sci-fi, Planet of the Apes is an imaginative and entertaining commentary on major parts of our current society. Or, in this case, 1960s American society. Segregation, anti-intellectualism and creationism are all dissected via the lens of one unlucky space explorer, Taylor (Charlton Heston), and his misadventures in a civilization where apes enslave humans.
Taylor, along with his two cosmonaut friends, Landon (Robert Gunner) and Dodge (Jeff Burton), are heading to Earth after a brief mission to space which has dilated time over seven centuries for the Earthlings. But after they bump something in the ship, they end up way off course: thousands of years wrong, and crash landing into a planet where the few humans are primitive mutes who are rounded up by troops of gorilla soldiers wielding muskets and flash photography.
Things quickly spiral into the surreal as Taylor and the others end up imprisoned by the apes. Already we see clear segregation: the orangutans are the scientists, the gorillas are the soldiers, and the chimpanzees are just trying to get by (especially after the "quota system" has ended - Affirmative Action?). After a wounded Taylor regains his voice, all hell breaks loose. He befriends two chimpanzee progressives - Dr. Zira (Kim Hunter) and Cornelius (Roddy McDowall) - who liberate him and send him off to discover the truth about this crazy planet's great mysteries.
The setting is rich and vivid. There's a great moment, for example, when Taylor is fleeing the guards and he ends up in a natural history museum - taxidermied humans are exhibited in various scenes "from the wild". The characterizations are also fascinating; Taylor and his astronauts chat at length about their old habits as misanthropes and lotharios. And we just loved the cheeky nudges to 1960s (counter)culture - at one point, Taylor shaves and tells a young sympathetic chimp that where he comes from, "only kids your age wear beards". The kid cocks his head, "Beards? I don't go in for fads." Cornelius chimes in: "Somehow, [clean-shavenness] makes you look less intelligent." Later on, Taylor jokes with the young chimp, "Remember: never trust anyone over thirty!"
A lot of a fun (and a lot better than the 2001 remake); it was clearly made with passion and intelligence. And some of the dialogue - especially Taylor's liberal use of "Damn you, damn you to hell!"s - is delightful. Now get your stinking paws off me, your damned dirty ape, and watch this damned film!