20th Century Fox/Kobal/ShutterstockWith apologies to Darth Vader, "Luke, I am your father" is not the greatest sci-fi film quote. (It's not even actually the quote; in The Empire Strikes Back, he says "No, I am your father.") The most iconic sci-fi line was first uttered 75 years ago, in a movie that came out more than a quarter-century before the first Star Wars. It's only three words long, but those three words decide the fate of the world: "Klaatu barada nikto."The quote comes from the classic 1951 film The Day the Earth Stood Still, one of the most beloved — and most intelligent — sci-fi movies of all time. Directed by Robert Wise, The Day the Earth Stood Still looks like an alien invasion movie at first glance, but it's something much more than that. Klaatu, an alien visitor played by Michael Rennie who lands his flying saucer on the National Mall, really does come in peace. Or at least, that's his intention. When he's injured by a nervous soldier upon exiting his spacecraft, his hulking robot companion Gort threatens to retaliate until Klaatu calls him off. As Klaatu recovers and befriends Helen Benson, a widow played by Patricia Neal, he explains the nature of his mission. Now that mankind has gained the power to destroy itself by inventing atomic weapons, it is a threat to the other civilized planets who live peacefully together. Should mankind continue down the course that has already sparked a Cold War, our planet could face destruction. (It's a clear, powerful metaphor.)Klaatu doesn't especially relish the idea of unleashing alien technology against the Earth, but he warns Helen. Should anything happen to him, she must tell Gort one specific phrase to prevent him from destroying everything: "Klaatu barada nikto." When Klaatu is killed, Helen must face the robot and hope that "Klaatu barada nikto" actually does something.The meaning of "Klaatu barada nikto" is never translated in The Day the Earth Stood Still; context clues suggest it gets Gort to call off his rampage and instead recover Klaatu. But the lack of an official translation of Klaatu's alien language makes the phrase that much more alluring. We don't know, exactly, what it means, but darn if it isn't fun to say. "Klaatu barada nikto" is a delightful combination of syllables that sound like nonsense but apparently decide the fate of the entire world. It's almost what's so great about science fiction in miniature, using fun, imaginative creations to talk about issues of real importance.Perhaps this special combination of the silliness of "Klaatu barada nikto" and the high-stakes context of the movie are what made the quote so memorable. In the three-quarters of a century since The Day the Earth Stood Still came out, "Klaatu barada nikto" has been referenced or included as an Easter egg in plenty of geeky media. Perhaps the most overt reference was in Sam Raimi's 1992 film Army of Darkness, where it's the three-word phrase Bruce Campbells' Ash needs to remember in order to stop the Deadite horde from resurrecting. (He can't remember it, of course.)There are additional homages to "Klaatu barada nikto" in the original Tron, the cheesy '80 killer robot movie Chopping Mall, Farscape, the Nickelodeon game show Legends of the Hidden Temple, Two and a Half Men, The X-Files, the video games Fallout 2, Minecraft, and World of Warcraft, Rocko's Modern Life, and Teenage Mutant Ninja Turtles, to name a few. Star Wars, the sci-fi franchise that has no shortage of iconic quotes itself, had a nice reference to The Day the Earth Stood Still's famous phrase hidden in Return of the Jedi. One of Jabba the Hutt's guards aboard his sail barrage was named Klaatu, a member of the Nikto species of alien. Another was named Barada, and he was a Klatooinian.Klaatu, a Star Wars alien named after The Day the Earth Stood Still who appeared in Return of the Jedi. | LucasFilmOne sci-fi movie that very nearly did not feature "Klaatu barada nikto" was the remake of The Day the Earth Stood Still. The first draft of the script didn't have the line at all, and Keanue Reeves, who played Klaatu in the 2008 movie, pushed for its inclusion. "That was actually something that wasn't in the script, and I said, 'You've got to have that,'" he said according to a Blastr report from the set. Director Scott Derkison, agreed, though the final version audiences heard is fairly garbled and distorted.The 2008 remake of The Day the Earth Stood Still is criticized for a lot of reasons, so it's not just the near-lack of "Klaatu barada nikto" that made it a flop while the 1951 original endures as a classic, beloved work of science fiction. But, when you've got a quote as good as "Klaatu barada nikto," enunciation certainly helps.The Day the Earth Stood Still is available to stream on Philo or rent as VOD.