It's not easy being an alien on Earth.
As if the usual shenanigans weren't enough, now your ship is critically low on phlebotinum, and all these benighted savages use is oil, gas and electricity...
But hey, what's this? Your sensor-bot beeps loudly!
The natives do have phlebotinum—they just don't know it.
Excitedly you tell your native friends about your discovery, but they just look strangely at you.
"What Do You Mean, It's Phlebotinum?", they ask. "That's PIZZA!"
Truly, these Earthlings are a silly lot.
To truly fit in this trope, the material should be of immediate use—serve as fuel, weapons, medicine, field repair parts, etc. If it's valuable as raw material or for monetary value, it's very close to an inverted Worthless Yellow Rocks, and should first be considered for addition there.
- Some incarnations of Venom of Spider-Man fame feed off of a chemical found in the human brain. Eventually Eddie and he discover that this same chemical is just prominent enough in chocolate bars to sustain him.
- One issue of MAD (back when it was still an anthology) had an alien whose planet was destroyed by unstoppable goo. Turns out it's strawberry Jell-O. He freaks out on realizing it.
- Similar to the Back to the Future example, "makers" (nanomachine hubs that can assemble almost anything) in Transmetropolitan can run either on "base blocks" of transmutable matter... or on garbage. Makers are quite cheap (well within the means of most upper-working class people), but the hyper-dense high-efficiency "base blocks" are so expensive most middle-class people can't afford them, and run their makers on street garbage collected before the garbagemen can come clean the streets.
- At one point in the Transformers comics, a deadly plague of metal-eating Cybertronian insects known as "scraplets" was devastating Autobot and Decepticon alike, until they turned out to be fatally allergic to a compound that was so rare on Cybertron that none of the Autobots had ever realised that humans referred to it as "water".
- In Monsters, Inc.., the monster civilization gets all its energy from... the screams of children. And the laughs, which are far more powerful.
- In Back to the Future, the "Mr. Fusion" attachment causes everything to become this — you can run your car on used coffee grounds and banana peels, and throw away that useless plutonium.
- Only when it's in flight mode, and only when it's traveling through time. It needs gasoline for a trip to the corner drugstore. Presumably the Mr. Fusion isn't compatible with the engine.
- Which is a bit of Fridge Logic, because apparently, in the future, people have 'hover conversions' of their older cars to make the car fly through the air solely by electricity that Mr. Fusion generate for free...but for some reason leave their internal combustion engines intact to drive the cars down the streets. Perhaps gasoline is also free, but wouldn't it be rather difficult to make the wheels tilt like that and keep the gasoline-powered engine and transmission hooked up, instead of just stripping out all that and attaching electric motors to each wheel? (And removing the engine would create a better place to put Mr. Fusion than sticking out of the back of the car.)
- Just so we're all clear, the DeLorean DMC-12 has its engine in the back of the car, and the "hood" is the trunk.
- Alternately, Mr. Fusion just powered the time circuits, and the hover ability somehow worked off the gasoline engine, especially when we see the smooth transitions between driving and flying. Although this seems to be even an odder premise.
- In the Carl Reiner movie Spirit of '76, a time machine sets off for 1776, but runs out of the fuel tetrahydrozeline, and ends up in bicentennial year 1976 instead; fortunately, they learn that tetrahydrozeline is the active ingredient in Visine eyedrops.
- In The Cat from Outer Space, the title character is looking for a few kilograms of a common (from his point of view) but unknown (to humans) substance to fix his spacecraft. Supposing that humanity calls it by a different name, he begins describing its properties to his scientist friend:
Frank: Wait, that's the atomic weight of gold.
- In My Favorite Martian, the eponymous Martian's spaceship has broken down, and is now missing a critical engine part. Much agonizing ensues as the Martian despairs of creating a new one... until he bothers explaining what it does. It's an alternator. He's then able to repair his ship simply by ripping an alternator out of a car and plugging it in.
- There's a short story about a friendly alien coming to earth and befriending some human children. He is seeking a legendary device that somehow knows how to keep hot things hot and cold things cold. He leaves happily with a thermos.
- Is the alien a Letonian, by any chance?
- How can one travel through space without this knowledge?
- In Dragon Bones, the story starts with Ward discovering the eponymous dragon bones in a cave. He just thinks it sad that a dragon was killed. However, he is later told that dragon bones, pulverized and in a drink, can make a powerful magician incredibly powerful, and even give nonmagical people magical abilities.
- In Married... with Children, Al's used socks keep getting stolen by space aliens. By the end of the episode, he discovers that they're needed for spaceship fuel.
- Apparently, his foot odor was Just. That. Powerful.
Alien Woman: It's only onlux!
- Crichton searches for a complex chemical compound as medicine for Moya. It turns out to be the local equivalent of salt on the planet on which they've landed.
- In a meeting with Scarran Emperor Staleek, Staleek mentions their "delicacy," the Crystherium Utilia flower, to John. Taking this to be a reverse Worthless Yellow Rocks situation, Crichton mentions that the flowers grow wild on Earth (the Bird of Paradise). What Crichton didn't know at the time was the the Scarrans were dependent on the flower to maintain their intelligence above that of a caveman. And that he just drew a big Scarran bullseye on Earth by telling them that. Oops.
- Star Trek: The Original Series:
- Inverted in the episode "City on the Edge of Forever", where Spock and Kirk are marooned on 1932 Earth, but Spock says that he "only" needs a fair-sized block of platinum in order to build a computer to prevent Godwin's Law of Time Travel from taking effect. Meanwhile, their job only pays 15 cents an hour. Spock doesn't know that platinum is fairly rare on Earth, and is completely unobtainable in such quantities.
- In "Elaan of Troyius", the crew discovers that Elaan's necklace is made of dilithium crystals, which power the ship. A bemused Elaan says her people had never heard of dilithium and saw the "common stones" as near-worthless, only made into jewelry because it is pretty.
- In an episode of Lamb Chop's Play-Along, the alien Zarc needs "zappelmeis"note to fuel his rocketship and get back home to Yzarc. As it turns out, "zappelmeis" is apple juice.
- An episode of Captain Kangaroo featured a stranded alien who desperately needed a "glump-full of gleedle" to fuel his ship. It turned out to be a glassful of milk.
- The Tales from the Darkside episode "Barter" (a parody of I Love Lucy) features an alien who needs ammonia desperately (he drinks it, so it's either food or medicine to him) and is willing to trade for it.
- In The Pirahna Club, main character Ernie works at a horrible fast-food joint. A foreign (Japanese, if memory serves) competitor realises that their fries are never as tasty as at Ernie's restaurant, and resorts to espionage to find out the secret. It turns out that there is grease from Ernie's incredibly old DeSoto in the frier. Hilarity Ensues as the spies attempt to buy, borrow or steal Ernie's car — which he loves and won't part with.
- The 1989 Teenage Mutant Ninja Turtles once helped a stranded alien to fix his spaceship and get home. At the end of the episode, he was only missing the ship's fuel source, "grutnyp". It turned out to be pizza.
- The premise of Sheep in the Big City consists of the military pursuing the eponymous sheep in order to power their "sheep-powered Ray Gun".
- Subverted in one episode of Futurama. Fry finds himself with a large heap of money and uses much of it to buy the last can of anchovies in existence, bidding against the mega-mogul Mom. Mom knows that anchovy oil can be cultivated as an incredibly cheap robot oil and reasons this is why Fry wants the can so badly. As it turns out, Fry just loves pizza with anchovies.
- In one episode of Mighty Max, it turns out that aliens want Earth's toxic and radioactive waste; it's apparently an extremely valuable commodity on their home planet. Win-win for Earth, Max and the aliens.
- Spider-Man and His Amazing Friends had an episode where travelers from the future needed three substances to repair their ship. Spiderman's friends identified two of them as rare compounds found in lava and deep ice water, respectively... the third turned out to be ivory.