Sheriff: Where? Swimming in the fountain of youth?!
Scott: Derek's been aged backwards. He can't remember anything. We just need to talk to him.
Some form of Applied Phlebotinum results in one or more main characters regressing to an earlier age. It may be the result of a freak accident, a plot on the part of the bad guys to incapacitate our heroes, or done on purpose so the characters can relive their childhood (at least temporarily). It may involve a Physical Attribute Swap with someone younger. Always central to the plot of a Baby Morph Episode, which is Exactly What It Says on the Tin.
For some reason, this plot is often used in Fan Fic where it's called a De-Aging story. Often combined with Raise Him Right This Time.
When it's an actual fountain or similar artifact that exists to restore youth, it's a Sub-Trope of Immortality. These will, of course, be sought out by Immortality Seekers. A downside to this version of the trope is that the fountain is usually stationary and often in a remote region, forcing the newfound immortal to permanently stay close to it or at least return regularly, and to keep it a secret from others due to Immortality Immorality.
When someone dies in his rejuvenated state, expect him to turn back old immediately.
When a Fountain of Youth effect doesn't get reversed and the younger actor replaces the older one in the cast for good, it's also an example of The Nth Doctor.
It's common for characters to overdo it in stories involving this trope, often winding up as babies, or possibly even suffering Death by De-aging. This may or may not be permanent, but if the character in question was a bad guy, expect it to be permanent; well, at least, until they grow back up the old-fashioned way.
If the character's clothes don't change with them in this event (and it's shown onscreen), it's likely to cause Shapeshifting Excludes Clothing. If the event is offscreen and thus a surprise to the audience or one or more characters, Empty Piles of Clothing results. This process may result in an Age-Down Romance when the youthened character gets infatuated with someone of their new age or vice-versa.
Compare Elixir of Life, a Sister Trope with some similarities to this one.
The Trope Namer is the mythical Fountain Of Youth that Ponce de Leon supposedly searched Florida to try and find - although this idea was not actually attached to his name until several decades after his death.
Contrast with Overnight Age-Up and Plot-Relevant Age-Up. Compare Really 700 Years Old, where an individual is vastly older than even the maximum natural lifespan for their species, and looks nowhere near as ancient as they actually are; Merlin Sickness, where the individual's aging progresses in a backwards fashion (i.e. they grow younger rather than older); and Longevity Treatment, where one's maximum lifespan is increased (which does not necessarily come with youth). See also Healing Spring.
- In this advertisement, a young man continues regressing from what may be a high-schooler, all the way down to pre-schooler.
- In a commercial for Nickelodeon in the late 80s, a scientist is trying out a youth potion to make himself a kid again so he can watch "Kids only weekend". But when he drinks it, he turns into a baby which the announcer says "Sorry babies are too young to watch "Kids only weekend"
- There were a couple commercials for the candy Baby Bottle Pop that featured this trope.
- Whenever kids were eating the candy their heads became that of a baby.
- In one, teens at a dance are bored and eat the candy and anyone who ate one is turned into a cartoon baby.
- In an ad for the PS2, we are shown the aftermath of this. In a nursing home, we see empty halls with discarded clothes with no one in sight. A clock is shown moving backwards and then we see naked babies crawling around.
- In a commercial for Bojangles, an old man shows off his Bojangles box. An old woman isn't impressed and drinks a water fountain to become young again and says "I found the water fountain of youth". We see the man again and he's not impressed. We then see the woman has turned into a girl around 13 and she walks away.
- In a commercial for Johnson and Johnson baby shampoo, we see a woman smiling at the camera and bubbles covering the screen. Every time this happens she becomes younger from adult to pre-teen to child and then to baby.
- A long-running series of commercials on American television for Frosted Mini-Wheats cereal had various adults stating to the camera their "serious adult side" approves of the cereal's nutritional value. Then they'd suddenly become children in oversized clothes and continue explaining, in the same voice, the "kid in them" enjoys the frosted sweetness. Sometimes they'd reverse the bit, with a child becoming an adult.
- There was a commercial for some sort of body wash where football players showering after a game using the product transformed (off-camera) into infants.
- This commercial for the South African drink Steri Stumpie suggests that the drink will cause a mother and son to get 10 years younger if they drink it at the same time. Unfortunately, in this case, the son happened to be a bit younger than 10 years...
- The city of Orlando did a series of commercials advertising its tourism (With the same family: one father and son, the other mother and daughter) where the parents are turned into kids for the duration of their stay, turning back when they leave.
- Pleasant Goat and Big Big Wolf: Joys of Seasons episode 9 centers on a fountain of youth when the goats need to save Mr. Slowy from dying of old age (he lied to them as payback for mocking his age) and Wolnie wants to restore her youth. There was no more water left in it because too many animals drank from it.
- Miniforce X: "The Witch's Curse" and "Go Baby Max!" features a witch alien who uses a pacifier that can turn anyone into a baby, including one of the Miniforce Rangers Max.
- Magic: The Gathering:
- Jhoira from one storyline was exposed to time-warped water that dramatically extended her lifespan after a horrible accident at Urza's Academy. By the events of the Time Spiral storyline, she is over 1000 years old but looks like a 19-year-old—an almost literal fountain of youth.
- Magic has had the literal card Fountain of Youth for the longest time. This is how Jodah, Archmage Eternal of the Academy of the Unseen, came to be several thousand years old by the time he met Jhoira.
- Yu-Gi-Oh!: Avance becomes younger when donning one of the Nekroz armor. note He also does this as Zefrasaber, Swordmaster of the Nekroz.
- One Charles Addams cartoon shows a group of children standing next to a fountain in a jungle, all holding metal cups and dressed as Spanish conquistadors. One of them is saying "So, great. We found the Fountain of Youth. Who's gonna sail the old tub back?"
- In one Dream of the Rarebit Fiend comic, an old man dreams that he takes some rejuvenating pills, but accidentally takes too many and ends up becoming a baby again.
- In one The Far Side comic, an old man drinks from a drinking fountain labelled "Fountain of Youth" and regresses back to a baby - or at least his head does.
- In one Jump Start comic, Marcy and Joe are buying both their infant twins a toy. They comment that because they have twins they have to buy two of everything. They then mention they have four kids, and the next panel shows them and their two older kids as babies the same age as the twins. They then comment they are a family of sextuplets.
- In a strip for Liō, Liō uses a time machine to go to the beginning. As a result, he is sent back to the womb.
- A Pocahontas tie-in comic has "Poncito" de León, the 80-90-something son of Ponce de León reaching Virginia in the fruitless search for the trope namer started by his father. He thinks he has finally found it when he mistakes Pocahontas for a rejuvenated local old woman that he saw earlier.
- In The Boss Baby: Family Business, Tim and Ted are given a serum that reverts them back to their ages from the first movie for the next 48 hours.
- Kronk's New Groove: Yzma claims to have created a youth potion which she has Kronk sell to the old people in the village. Subverted in that the potion is a fake and the old people stay old. It does, however, work as a Magic Feather at making the old people feel more energetic.
- Secret Magic Control Agency: Among the potions at Ilvira's warehouse is one called Fungus Shrinkillus. Hansel, Gretel and the cookie dog all get splashed with it, turning them into children and a puppy. This creates a large hurdle in completing their mission, since they can't get any help from the rest of the SMCA due to just being mistaken for random kids.
- In Tangled, originally it was the magic flower that Mother Gothel used to keep her young. But after the Queen drank the flower and gave birth to Rapunzel, Gothel got her Fountain of Youth from Rapunzel's hair.
- In Turning Red, Ming is temporarily reverted to a teenager in the astral realm.
- In Yellow Submarine, The Beatles and Old Fred regress to childhood and young adulthood respectively after travelling backwards through the Sea of Time. When they end up reversing the change, they end up reversing it a bit too much.
- This is the point of 17 Again (2009). Mike falls into the river, and comes out of it in his 17-year-old body.
- Avengers: Endgame: When trying to make time travel work, Bruce Banner accidentally turns Scott Lang into a teenager. Then an old man. Then a baby.
Steve: ...It's a baby.
Banner: It's Scott!
Steve: As a baby!
Banner: He'll grow!
- In Before I Hang, Dr. Garth and Dr. Howard succeed in developing a serum that will reverse the effects of aging and decide to test it on Dr. Garth immediately prior to his execution. The serum's effect on his body causes Dr. Garth to collapse. When Dr. Garth awakens in the prison medical ward, he discovers that the serum has reversed some of the effects of aging on his body, including the graying of his hair, the appearance of his face, and his physical fitness.
- Beautifully played with in the finale of the IMAX short Cirque du Soleil: Journey of Man: When The Everyman middle-aged hero accepts the old bowler hat of his youth from a little Vagabond Girl and ducks offscreen so she can put it on him, the voiceover narration explains "Years turned to dust. I was young again." He rises back into frame as an old man but it's clear he's as full of life and joy as he's ever been, having regained his youthful spirit, making this an example of this trope and Overnight Age-Up at the same time!
- The pool house in the movie Cocoon, by way of Alien Phlebotinum.
- In The Dark Crystal, the Skeksis use the light of the Crystal, focused by a reflector, to drain the vital essence of other creatures into a liquid form that they can consume to restore their youth. Podlings restore youth for a handful of seconds. Gelflings restore it for a longer period, but the rejuvenation is still ultimately fleeting. The Skeksis exterminated nearly the entire Gelfling race due to a prophecy, resulting in a shortage of supply.
- In Faust, Faust, who is an old man, makes his original Deal with the Devil for altruistic reasons, to save the people of his town from The Plague. When the townsfolk figure out the demonic source of Faust's powers and cast him out, he gets a lot less altruistic, demanding youth so he can enjoy sensual pleasures. He gets it and does.
- The Fountain involves a story within a story about a Conquistador's quest for the Tree of Life, which can theoretically grant immortality. Outside the frame, there is a tree which essentially de-ages a cancer-ridden monkey and presumably grants immortality to the main character.
- HOUBA! On the Trail of the Marsupilami: A special orchid's juice can be distilled into a youth potion. The Marsupilami being apparently linked to those orchids, the Big Bad is after it. He eventually gets his youth back, plus interest.
- In Jupiter Ascending, a special fluid called RegeneX restores your youth when you bathe in it. Unfortunately, it's produced by killing and processing people. Kalique takes Jupiter to her bathing chamber to demonstrate it to her, submerging herself into a pool and then slowly emerging from it, now young and beautiful.
- Early on in the French film Les Visiteurs, a witch forces an old woman to drink one of her potions. This causes her to inflate slightly and rocket through the roof (And judging from the other holes in the roof, she wasn't the first victim), only to fall back in the house a minute later, as a younger woman.
- The Little Rascals short Shrimps for a Day involves a wealthy young couple who find a magic lamp and wish themselves into kids so they can play with the Rascals, who are visiting from an orphanage. Naturally, things go horribly wrong, and they get a first-hand view of how badly the orphanage is really run.
- In the last scene, Spanky wishes the mean headmaster into a little kid his own size, and proceeds to give it to him but good.
- Miss Granny: 74-year-old Mal-soon, depressed about being old, goes into a photography studio for a picture. The photographer promises "I'll make you look 50 years younger," and he does, by casting some sort of spell that turns her to her 20-year-old self.
- The MacGuffin in Nutty Professor II: The Klumps. Professor Sherman Klump creates a fountain of youth formula which lasts temporarily.
- Once Bitten: Blood from a virgin keeps vampires looking young. The female vampire antagonist needs a male virgin, and they're in very short supply in her area.
- The Sequel Hook at the end of Pirates of the Caribbean: At World's End ends with (the immortality-seeking) Jack unfolding a map to something called the "Agua De Vida". The book that the next movie is based on revolves around the Fountain, so...
- The Fountain in Pirates of the Caribbean: On Stranger Tides is played with. It doesn't make you any younger, but instead adds years to your life. However, you need someone to take the years from...
- In the new version of The Shaggy Dog. Kozak's plan is to obtain the DNA of the dog Shaggy, to create an immortality serum and make humans have eternal youth. He shows Strictland the genetically experimented snake in the laboratory, the snake rejuvenated thanks to the canine serum, but with side effects like having a dog's tail and canine behaviors.
- The MacGuffin weapon of the Big Bad in Sky High (2005) did exactly this. The Pacifier seemed to have only a 6-to-12-month-old baby setting, or that's what Royal Pain had it locked on.
- Smurf-essence becomes this in The Smurfs when Gargamel used it on Odile's mother, which makes Odile want to get her hands on it.
- The planet Baku in Star Trek: Insurrection. The fact that it remains unused by the rest of the Federation and is only used by the Baku makes it seem much like a Not So Hidden Elf Village.
- In The Three Stooges short "All Gummed Up", the boys are druggists who invent a youth serum and give it to their elderly landlord's abused wife. Predictably, she turns into a beautiful young woman. But when the landlord tries it, he turns into a little kid (who still has a beard!). Chasing after the Stooges, he trips and falls and throws a tantrum with dubbed-in baby crying.
- In the remake "Bubble Trouble", the landlord turns into a gorilla.
- Twice-Told Tales: In "Dr. Heidegger's Experiment", Heidegger believes that the water dripping into Sylvia's coffin has the power to preserve. He tries it on a withered rose and it comes back into full bloom. Carl and Alex drink it and become young again. Carl injects the liquid into Sylvia and she comes back to life.
- In Wishmaster 2: Evil Never Dies, one of the burglars who broke into a museum meets the Djinn, who grants him one wish. The burglar, scared out of his wits, wishes he were never born. The poor guy really should have known better than to ask that of a Jackass Genie. The Djinn is all too eager to grant his wish, causing the guy to age backwards until he flat out disappears, only leaving his clothes behind.
- Also the plot of the 1986 Disney made-for-TV Keanu Reeves movie Young Again, from which 17 Again seems to be heavily drawn. A mysterious man grants Michael Riley's wish to be young again. It doesn't work out the way Michael expects, and like many a Disney film, Michael's only way to return is to be content with what he had.
- The Fountain of Youth is alluded to in "Loving You's a Dirty Job (But Somebody's Gotta Do It)" by Bonnie Tyler.
- Daniel Amos: In the short story that accompanies the album ĦAlarma!, one scene involves an entire church congregation reverting to babies before the narrator's eyes. This was meant as a satire of certain real-life Man Children.
- Faith No More: The music video to "Sunny Side Up". Apply The Power of Rock to a retirement home...and the pacemakers blow to kingdom come. General Surgeons Warning: Won't last forever.
- The video for Foster the People's "Helena Beat" has the frontman's character getting kidnapped by a pack of wild children and strapped to a contraption with an old man at the other end. The machine saps whatever youth the old man had left and transfers it to him, turning him into a child. One wonders if all the other kids in the pack didn't arrive by similar fates.
- Nart Sagas: eating the special apple from atop the golden tree will cause a person to grow younger with each passing year instead of older, among other powers.
- The four players in the Cool Kids Table Harry Potter-themed game Hogwarts: The New Class are de-aged back to eleven so that they can go through Hogwarts and learn magic naturally.
- The Alien Worlds episode "Time Clash" had Jon Graydon and Buddy Griff becoming children again while using a time machine.
- The finale of the early Cirque du Soleil show Nouvelle Experience had the inhabitants of a Magical Land change The Everyman hero back into a child.
- Dungeons & Dragons:
- The older editions featured the Potion of Longevity and Elixir of Youth, which do what their names indicate. The former is more powerful - de-aging by up to 10 years instead of just 4 - but overuse can cause all of that lost age to be brought back at once, whereas the latter rejuvenates legitimately and permanently.
- Dragon magazine
- Issue #5 article "Witchcraft Supplement for Dungeons and Dragons". The Priestess witch spell Youth reduces the age of a living creature by forty years or two creatures by twenty years each.
- Issue #60 article "Gods of the Elves". The elven deity Labelas Enoreth can reduce a creature's age by up to 100 years, but only once in its lifetime.
- Priest spells. The spell Curse of Yondalla causes a living creature to become an infant again. Unless the curse is somehow removed, the creature will grow up normally.
- Mentioned in the backstory of Heroscape as one of the side effects of drinking from a Wellspring, the other perks being enhanced strength, magic, and prophetic visions.
- Warhammer 40,000:
- For the Imperium of Man, "juvenat treatments" are available to the wealthy and to valued Imperial servants. These extend the human lifespan, with repeated treatments capable of extending a human lifespan to several centuries and keeping a person hale for most of that, though they seem to have a hard cap at about five centuries, though this is largely up to author fiat. There had once been the implication that these were made from actual juveniles, but the concept never caught on; in an ostensibly Grimdark universe, this was one of the instances of "Grimderp," and was never pursued or brought up again.
- Other forms of preservation also exist. Astartes super soldier implants, the artificial organs and process used to make Space Marines extends the human lifespan to several centuries before juvenat treatments (and there's some circumstantial implications that the two are incompatible).  bloodlines of Space Marines are particularly notable for longevity, as Dante, current Chapter Master of the original Blood Angels, is more than a thousand years old, and still kicking ass as an old super soldier.
- The Adeptus Mechanicus, on the other hand, replace their flesh with cybernetics, and with juvenat treatments, can extend their lives to millennia. To complicate things, they also can use cloning to replace their biological components, which is especially handy when certain cloning techniques fully enforces Genetic Memory.
- Chaos Marines have a cheat. While the influence of the Dark Powers can extend their life to many millennia, for the most part, they mostly live within Warp anomalies, which means time doesn't pass quite the same way. A Chaos Space Marine might fight one war, retreat to their home for a few subjective decades to build up again, and reemerge to find that centuries have passed in sections of realspace where Warp anomalies don't exist.
- For the Eldar, expanding their psychic powers also has the curious side-effect of extending their lifespan. Eldar, in the Craftworlds at least, run a society that's not quite caste-based but highly departmentalized; those who take a job on the Path of the Seer, or Warlocks, actively train their powers, and those that become lifers in this job, accidentally or otherwise, become Farseers, who can live for millennia until death in battle or they succumb to the career-specific physical breakdown of their bodies turning to crystal. The average Eldar lives about a thousand years before dying of old age, and one particular Farseer, Eldrad Ulthran, has staved off turning to crystal to live for at least eleven or twelve millennia.
- Dark Eldar have a different cheat. They don't allow for psychic powers other than a type of vampirism to suck up suffering of other beings, so they have evolved into a piratical society based around an insatiable slave trade. This kind of "feeding" can extend their life indefinetly, but requires more and more feeding the older they get.
- The Fountain of Youth is featured in Indiana Jones Adventure at the Disney Theme Parks. At the end of the ride, Sallah mentions that they have strollers available for anyone who drank too much from it.
- Gilgamesh from Fate/hollow ataraxia did this with a youth potion because, apparently, "this whole mess is stupid, screw you all". All the more hilarious, considering that he's been a tyrant (in the past), not to mention a dog-kicking Knight Templar and Big Bad who wanted to unleash a terrible curse on humanity because only those who could survive it were worthy of being ruled over; when he reverts, he turns into a cute little boy that everyone loves.
- In Radical Dreamers, this is an important plot point: Kid is revealed to be Schala from the previous game: After the Ocean Palace incident, she was overcome by grief and guilt over what her actions had caused. The Frozen Flame picked up on those emotions, and responded by transforming her into a baby, erasing her memories, and sending her to the modern era, where Lucca found her and raised her. Granted, this game is not canon anymore, but an easter egg from Chrono Cross implies that the events of Radical Dreamers actually happened in another dimension, and one of the many ending cutscenes in Chrono Trigger DS actually does show Lucca finding baby Schala/Kid and adopting her.
- In Autumn Bay, Captain Jack Bishop, leader of a team of specialists dedicated to containing supernatural threats, is turned into a teenage girl by one of their targets.
- In Decrypting Rita, after Rita the Hat Lady re-emerges into her native universe from the depths of the Panopticon, she ends up in a body much younger than her previous one. She even gains a new hat to match.
- In Doc Rat, heavy duty anti-ageing cream regresses a bird back to an egg.
- The Dragon Doctors:
- A team of magical robbers are trying to steal a large drum of rejuvenating fluid in the "Thieves of Life" arc. An acid booby trap cracks open the drum, however, exposing one of the thieves to an overdose of the fluid, immediately transforming her into a baby.
- A Backstory chapter features a lake of youth that is responsible for the 'deaths' of several colonists. It's basically a Deconstruction of the Fountain of Youth: the lake is hidden because everyone who goes near it dies. Nothing grows around it because it causes everything to un-grow, so it's a desolate wasteland. Even contact with the vapors from it can erase years or decades of age from someone, so most people who get close wind up vanishing into Empty Piles of Clothing (which, incidentally, is the Trope Namer for that). The discovery of that lake was actually what enabled the development of the previously mentioned rejuvenating fluid after people figured out how to harness its effects.
- In El Goonish Shive, Dr. Germahn invented one.
- Morgan of Gender Swapped after pestering Sven long enough to bend the rules for the two of them.
- In one strip of Hetalia: Axis Powers, England de-ages Korea to make him less annoying. In a later April Fool's Day event he does it again to France.
- In Jix one of Lamerix's inventions instantly changes one's age, she loses it in the couch cushions and Lauren is accidentally turned into a child after sitting on it, though she eventually reverses it. Later on, she uses it to turn Aragara, who had been artificially aged by growth hormones back into a kit.
- Karin-dou 4koma: Seren and Elza's independent attempts at weight-loss magic actually turn them into children. Seren eventually turns herself back, but Elza prefers her new form.
- In Kevin & Kell, the vulture family has a time machine where they sometimes travel to the past. But in some cases, if used right, it can affect someone's age.
- Dolly, a clone of Corrie, begins to age faster than usual. A new identity is created for her and she gets a job as a cleaning lady for the vultures. While cleaning she accidentally activates the time machine and is turned into a baby where she remains still.
- In other strips the characters are briefly turned into babies for laughs, but these are probably not canon.
- A Meta heavy instance happened in Level 30 Psychiatry. With the assistance of Carmen Sandiego and her Impossible Thief skills, Dr Gardevoir removed the popularity of the Gardevoir species from the internet so she could browse in peace. Unaware that she is in a webcomic, this led to her De-Evolving into a Kirlia.
- Emily from Misfile suffers from this, though she was only regressed by two years rather than the usually much larger amount. Since she was just about to turn 18 and had received her acceptance letter from Harvard these were a rather vital couple of years though.
- Ponce de Leon and his companion look for one in Oglaf, but only come across the fountains of Doubt,
DeathWater So Good Even Dead People Want It, and Girl (NSFW).
- In Opplopolis during Luke Dugans' interview with Shirley Kidd about a mysterious movie she appeared in called Marvedyne (that word being the series' MacGuffin), the latter suddenly de-ages from 60-ish to 20-ish with thus far no explanation, though there was a conspicuous cup of coffee earlier in the scene.
- Mini Mari!! kicks off when Marisa Kirisame eats a mushroom that reverts her back to the body and mentality of a child.
- The Kids arc of Roommates where the resident magical troublemaker Schmuck Baits ("What does this glowing orb do?!") the other main cast members into this and we learn that some people changed a lot... others not so much. Thank god the magic only lasted thirteen hours.
- Saturday Morning Breakfast Cereal: The "It's a literal fountain people seek" form is deconstructed in "Life":
"Would you like to go back to the angry teens, the confused twenties, the anxious thirties, the crisis forties, the cynical fifties, or the aching sixties?"
- In True Villains, old, wizened Evil Sorcerer Bayn Pheonix is transformed into a kid by demon Xaneth Antaris so Bayn cannot surpass him in power.
- When Mingmei in The Wotch discovers that she used to be Dr. Sorgaz, everyone assumes that she would want to be turned back... except the Sorgaz persona himself, who basically takes it as a second chance in life, and instead opts to merge with Mingmei permanently.
- Not to mention 21-year-old Evan's frequent temporary escapes into a 4-year-old (female) body, called "Lily".
- Seriously, what about the entirety of Adventures in Babysitting? Even though Evan turns into an adult female, Anne, Robin (Robyn?), and Jason were turned into children (Okay, they turned into the opposite gender too, but that hardly matters!)
- Duncan/The Annihilator from The Young Protectors literally becomes a youth for his end of the deal desiring youth with Laampros.
- Karekore The Half Blood: Kage is turned into a young boy after being given a poison by a gang member while he was unconscious. However, he kept his original personality after his appearance changed.
- In the My Little Pony: Friendship Is Magic abridged series Friendship Is for Adults, Luna is reduced to taking the form of a child, after the Elements cleanse her of evil in the pilot. (In the original she became relatively small, but that had been her earlier form anyway.) Unlike canon, she is also left with amnesia and instead of being back to her adult form in her next appearance, she seems to be stuck like this and Celestia is left to take care of her now juvenile sister.
- In the aptly-named "Baby Boom" episode of Gotham Girls, Harley is accidentally regressed into a baby.
- The Innocent: In the end, Thai children build a missile containing this to throw onto Saudi Arabia. They also sell one to French children, who throw it onto the Czech Republic.
- Renegade Rhetoric, a Character Blog for Cy-Kill from Challenge Of The Gobots with many posts consisting of describing the events of episodes from a non-existent second season of the cartoon, featured the legend in the post describing the fictional episode "Going Loco", where the Robo Rebels and the Guardians' human allies visit a ranch that turns out to be where the fountain of youth is located and the staff turns out to be historical figures Wild Bill Hickock, Davy Crockett, Calamity Jane, Jesse James, Annie Oakley and Ponce de Leon, having all used the fountain's water to keep from ageing.
- SCP Foundation:
- SCP-006. It's stated that O5s are only allowed to know that it is such a fountain and that non-Overseers are to be told that it's highly toxic water. Anyone not an O5 who is exposed to the water gets to experience the joy of being confined, studied, and executed by the Foundation so that they don't make it out alive with the knowledge of what SCP-006 really is.
- The abridged series Ultra Fast Pony reveals that sexual reproduction itself has been rendered obsolete by the ability to just turn adult ponies back into babies if need be. Naturally, after three little fillies learn this, they immediately turn The Mane Six back into children for fun.
- Whateley Universe example: retired U.S. Navy officer Sam Everheart was injured trying to save a scientist from bad guys. The 'hive' of nanites infected him and saved him... by turning him into someone a lot younger. He now looks like his deceased 17-year-old daughter.
- Rufus finds it in Episode 23 of World's Greatest Adventures... it's a sink. One tap for aging water, one tap for rejuvenating water. Guess which one he drinks from.
- Boochi is an NPC from a random event on the virtual pet site Neopets. He is a Baby Bruce who has a ray gun that turned players' active Neopets to the Baby paintbrush colour on a successful hit. As of March 29, 2014, Boochi can no longer turn Neopets the Baby colour, although he still appears as a random event. He just always misses.