A character grows up being oblivious to the fact that they're not the biological child of one or both their parents. Then comes The Reveal: the character's parent(s) finally tell them the truth about their parentage. The reasons for keeping this a secret vary; perhaps the parents felt the child was not ready to hear the truth (especially if their biological family or the circumstances of their birth are profoundly unpleasant), maybe it was to protect them, they could've sworn to the birth parent(s) not to reveal the truth, or a combination of these things.
How the character reacts can vary, often depending upon how their supposed parent breaks the news. For example, the character will probably react better if their parents tell them "We adopted you but we love you as our child regardless" compared to, say, the man they believed was their father snapping at them "You're actually the result of my wife's affair and I want nothing more to do with you." Context is key here. The character may experience some Adoption Angst or Bastard Angst.
A sub-trope of Deceptive Legacy. Don't confuse with I Have No Son! or That Thing Is Not My Child!, which is where the child is related to the parent, but the parent has disowned them. Also, this is not simply a subversion of Luke, I Am Your Father; this trope only applies if the non-father was actually believed to be the father. Compare and contrast with You're Not My Father. See also Family Relationship Switcheroo (which occasionally overlaps if the character's adoptive parent is related to them, just not in the way they thought).
Usually has nothing to do with I Am Not My Father.
- In the fifth episode of Mobile Suit Gundam Wing, Vice Foreign Minister Darlian admits to his "daughter", Relena, that he is not her real father while lying on his death bed after being assassinated in a false-flag bombing by Lady Une of OZ. He says she is really from the deposed Peacecraft family that ruled the Sanc Kingdom.
- In more than one incarnation of Superman's origin story, young Clark Kent is blissfully unaware that he's an alien from the planet Krypton until he comes of age and Martha and Jonathan show him the space ship.
- In Violine, Francois reveals that Marushka, who claimed to be her mother, was actually his governess, and her REAL mother is missing in Zongo.
- This◊ Bad Habits strip.
- Half an example occurs in the fanfic The New Retcons, where Michael Patterson discovers that John was not his biological father, and had in fact adopted him when he married Elly
- In Empath: The Luckiest Smurf, Brainy learns to his dismay and after years of idolizing Papa Smurf that he is not Papa Smurf's only biological son, but rather his half-brother Empath is. Brainy, like all the other young Smurfs his age in the village apart from Empath, were all Happily Adopted, though he was given specifically to Papa Smurf by his mother, who was Papa Smurf's wife.
- In Neither a Bird nor a Plane, it's Deku!, Inko and Hisashi are forced to have this conversation with their son Izuku after the latter's Kryptonian Super-Hearing allows him to overhear the fact that he should not have superpowers.
- The Love Club: Before dying, Frexspar tells Elphaba a secret that he's held for over twenty years: she isn't his biological daughter.
- In Kung Fu Panda 2, Mr. Ping, a goose, finally admits that his son Po, the titular panda, is adopted. He's shocked that Po already figured it out but just never mentioned it.
Mr. Ping: You... might have been... kind of... a-a-adopted.
Po: ...I knew it!
Mr. Ping: You knew?! Wha- Who told you?!
Po: No one! I mean, come on, dad!
Mr. Ping: But if you knew, you didn't you ever say anything?!
Po: Why didn't you say anything?!
- In Disney's Hercules, after Hercules ends up smashing up a lot of stuff in town because he can't control his strength, his mortal father decides to tell him that he's adopted and gives him the medallion with the symbol of Zeus on it, which leads him to the temple.
- Monty Python's Life of Brian:
Brian, Mr. Cohen wasn't your real father.I never thought he was, Mum.
- In Thor, Loki becomes suspicious after a touch from a Frost Giant doesn't burn his skin but colours it temporarily blue. He confronts Odin, who tells Loki that he was found by him in the aftermath of the great battle against the Frost Giants as an abandoned infant and that Odin took Loki hoping that he could bring peace between Asgard and Jotunheim through him. Loki doesn't take this well.
- Played for Laughs in The Jerk. Navin was raised as an Oblivious Adoption, despite the fact that he's white and his adoptive family is black. He's shocked when his parents reveal the truth:
Navin: "...You mean I'm gonna stay this color?"
- The protagonist has a moment like this at the end of Shades of Grey (though it's the result of illegitimacy, not adoption).
- In the Star Trek Expanded Universe novel A Stitch in Time, Garak remembers coming home to his dying father's side. Over his mother's objections, his father reveals that he's actually his maternal uncle, paid by Enabran Tain, Garak's real father and the head of the Obsidian Order, to maintain the ruse. Interestingly, the episode of Star Trek: Deep Space Nine that first reveals this to the audience has Tain denying the claim in this manner at first until Garak begs him to speak the truth for once in his life.
- Discworld: Carrot Ironfounderson, despite being six feet tall, needs it explained to him that he was not in fact born to the dwarves who raised him. His adoptive father wonders if the wolves in a Raised by Wolves scenario have to go through the same talk.
- In Deep Secret, Nick is rather shocked to learn that his mom is the Big Bad and the man who raised him is not his real father—in fact, his birth dad is the recently-murdered Koryfonic Emperor. He's visibly relieved when he finds out that obviously his adoptive father still plans to raise him, despite his mom's death.
- Supernatural, episode 4x10, "Heaven and Hell." Anna Milton discovers that her parents are not her real parents, and she is in fact a fallen angel that was reborn as a human.
- In the Syfy mini-series Tinman, DG's parents revealed to her that she's adopted and that they're actually robots.
- Parallax: Jeremy is not Ben's father. Veronica and Jeremy already knew this, but the rest of Ben's blood relations didn't. Of course, the truth was just too damn weird for anyone not Veronica to accept.
- In the Syfy series Haven, Chief Wuornos tells Nathan "I'm not your father" after Nathan confronts him about his Trouble being the same as Max Hansen's.
- Legend of the Seeker: After Ren asks how his father could sell him to the D'Harans, this is the response he gets. It seems he only married Ren's mother (though were not told why-perhaps he was promised a high dowry as a bribe to cover up her extramarital pregnancy).
- In the Red Dwarf episode "The Beginning", a hologram of Rimmer's father reveals that Rimmer's biological father is actually Dungo, the family's gardener.
- Phoenix Wright: Ace Attorney Spirit of Justice invokes a variation of this trope: since the adoptive father of Rayfa Padma Khura'in is dead, a Wham Line by another character (her brother whose relationship is then uncovered) proceeds to tell that no, that guy is not her true father. Her real father is long dead, and much to the young lady's horror, he was killed by her adoptive father.
- Subverted in Tales of Symphonia. It's likely that Frank actually is Colette's biological father; Remiel lied when telling Colette that he was her true father.
- Dragon Quest IV, at the beginning of the Hero's chapter.
- Dragon Quest V: None of the Heavenly Brides have real parents, and are actually descendants of Zenithians.
- Princess Maker 4: Going through the correct events will result in Patricia learning that the Demon Lord is her biological father and rushes home, gripping her father's arms and begging him to tell her that it's not true. Shortly after that scene, though, it makes no difference to Patricia because she still loves her father.
- Super Mario RPG: Frogfucius dramatically reveals to Mallow: "You... are not a frog!" (Since Mallow is a walking cloud creature, the audience isn't surprised.)
- Everyone else at Tadpole Pond is shocked. Complete with scare chords accompanying the reveal.
- Gun has the main character find out that the man who's raised him since infancy and trained him in hunting and gunfighting isnt his father at all, moments before said man is killed in an outlaw attack. The early parts of the game revolves around figuring out who his real parents were. They were a white frontier doctor and an Indian woman, who were murdered by the Big Bad for their knowledge of an enormous treasure. The man who raised him had in fact been working for the Big Bad as a guide, only to be betrayed when he attempted to stop the massacre.
- In Assassin's Creed: Odyssey, during the Misthios' confrontation with their father Nikolaos, one of the revelations he drops is that he is not your true father. As it turns out, their father was none other than the mathematician Pythagoras.
- In the Ben 10: Omniverse episode "The Rooters Of All Evil", it is revealed that Devin Levin isn't Kevin's father but an illusion implanted by The Rooters.
- Buzz Lightyear of Star Command spoofed its own source material this way by having Zurg claim he's Buzz Lightyear's father to distract him long enough to knock him out. Then, once Buzz awakens, Zurg tells him he was just toying with him.
- Briefly spoofed in The Amazing World of Gumball episode "The Code" with this exchange between Richard and Darwin (who is very well aware of his adopted status)
Richard: Kids. I have something to tell you.
Darwin: (dramatically) YOU'RE NOT MY FATHER!?
Richard: (also dramatically) HOW COULD YOU HAVE GUESSED!?
- Star vs. the Forces of Evil: In the third season, Moon and Star find out in one of the worst ways possible that their supposed ancestor Eclipsa, and by extension, any queen who came before her is not related to them at all due to the fact that she had a daughter with her monster lover, and the Fantastic Racism of Mewni and the High Commission resulted in said daughter being replaced with an average girl and stated in the records to be her daughter that she had with her Mewman husband. Even Eclipsa herself seems disappointed in the fact that she isn't related to Moon and Star.
- In Family Guy, Peter learns shortly after Francis' death that he wasn't his biological father. Played for Laughs when it's revealed that Francis never concealed this fact, Peter was just too dumb to realize it.
Young Peter: Happy Father's Day, Dad.
Francis: I'm not your father!