With the best of intentions (usually), your mentor or someone else you trust has been less than honest with you. Maybe he told you a half-truth, maybe an outright lie; maybe he just never mentioned something critical. Either way, you're about to learn the whole truth from someone else — and probably in the worst way possible.
Be extra-prepared for this one if there's a lost relative in your backstory. Especially if it's a parent. And especially if it's a parent you loved dearly but don't remember much about.
In some cases the lie is such that fans suspect the writer is actually trying for a subtle Retcon, but it's usually impossible to be sure about that unless you're the writer.
This trope tends to be spoilery; read the examples at your own risk.
- Emiya Shirou of Fate/stay night has these moments throughout the series. His father, Emiya Kiritsugu, only told him that he was a magus; the rest, and there's a lot, comes out mostly through Saber and Kotomine. For instance, Shirou knows his father saved him from a fire, but it's Saber who tells him that the fire was caused by the previous Grail War (in which she was Kiritsugu's Servant).
- Further comes to a head in the Heaven's Feel route where he has heard the name Einzbern, leading to Saber blurting out Kiritsugu's name... And prompting Shirou to request a detailed info dump, from both Saber and then Kotomine, making him more aware of the bigger picture, much earlier in the conflict.
- Mostly played for laughs with the titular Reborn in Reborn! (2004).
- Certain comics characters, usually team leaders, tend to keep secrets that get revealed via this trope. Niles Caulder of Doom Patrol, Professor X of X-Men, and Raven in the early days of Teen Titans are good examples.
- The eponymous hero of Scott McCloud's Zot! has a memorable Is That What They Told Me moment. His parents died when he was young, and they knew who would be coming for them: the assassin J9AC9K (read nine-Jack-nine). Rather than try to explain this to a child, they made up a Nursery Rhyme with Jack's name in it. When Zot first hears about Jack years later, he remarks on the tastelessness of an assassin taking his name from a nursery rhyme... and realizes the truth when the others don't recognize it.
- Dream from The Sandman says this when he encounters someone calling himself the Sandman and laughs himself silly. "You? You are the Sandman? Is that what they told you, little ghost?"
- Homura gives Kagami a condensed explanation of what she's doing in her universe early on in Stars Above. A few chapters later, Kyubey reveals that said explanation left a few important details out...
- Happens to the four in With Strings Attached. They're told different stories about the history of the planet C'hou, specifically the curse on Ketafa and the significance of the Vasyn, until finally they hear the real story of the curse and the real significance of the Vasyn. Slightly subverted in that everyone who told them a story sincerely believed they were telling the truth. Even Jeft.
- Star Wars: The most famous example is Darth Vader telling Luke he's his father in The Empire Strikes Back, contradicting what Obi-Wan had told Luke in A New Hope. Of course, Obi-Wan had already contradicted much of what Uncle Owen had told Luke. The boy really has a hard time getting the truth from others.
- Magneto says this almost verbatim to Pyro in X2: X-Men United ("Is that what they say?"), regarding him being "the bad guy". It wasn't a lie, so much as a point of view.
- Harry Potter suffers this trope on a regular basis.
- Dumbledore tells Harry at the end of the first book that his father, James Potter, once saved Snape's life. Not until the third book does he learn — from Snape — that James's friend was responsible for Snape's life being in danger to begin with. He also left out the fact that, rather than just being enemies like Harry and Malfoy, James and his friends regularly bullied Snape — despite being a Gryffindor, James seems to have been the Malfoy in this comparison, albeit a Malfoy without the racism and bigotry which Snape more than fully carried.
- In manner and timing, Harry finding out who revealed part of the prophesy to Voldemort.
- For timing, the nature of the "weapon" being guarded in the Department of Mysteries.
- Dumbledore never mentioned it to Harry that he might just end up having to let Voldemort kill him in to save the Wizarding World — but, thankfully, he gets better.
- In The Genesis of Shannara, a demon saying this to Kirisin leads him to realize that Tragen was actually a shape-shifting demon
- In Industrial Magic, rogue witches under the employ of Savannah's sorcerer father ofter to help Paige (Savannah's guardian) perform the Menarche Rites that will unlock Savannah's full magic power. Paige is then told by the rogues that the Rites she was taught was a nerfed version of the real thing: The witches themselves had created a lesser version, in order to keep themselves better hidden. Paige is not happy about this discovery.
- Bulldog is on the receiving end in the Battlestar Galactica (2003) episode "Hero".
- The secretive Garak of Star Trek: Deep Space Nine caused a few of these, usually for Dr. Bashir. In "The Wire", he tells Bashir several conflicting stories about his past in the Obsidian Order, all involving his friend Elim... which, Bashir ultimately finds out elsewhere, is just Garak's first name. Granted, Bashir pretty much knew Garak was lying the whole time, and the reveals about Garak in general fail to elicit the dramatic response on Bashir's part normally associated with this trope.
- Similarly, in Doctor Who, people who encounter the Doctor often end up finding things out the hard way. Depending on the particular Doctor, this can be anything from manipulation to simple carelessness.
- A rare good guy example is Charlie in the third season finale of Lost. He uses the fact that Ben lies a lot to mess with the heads of his captors.
- Another instance involving Ben's lack of truthfulness is when a captive Sayid tells Alex that she looks like her mother. Alex says her mother is dead, to which Sayid replies, "I'm sure that's what they told you."
- In Once Upon a Time 2.11, Captain Hook says this to Belle while holding her at gunpoint, and then reveals a fact Rumplestiltskin left out when he told her about the Love Triangle between himself, Hook, and Rumple's ex-wife, Milah. Rumple killed her.
- This happens twice in Jade Empire, first with Sagacious Zu and the Water Dragon telling you, then you telling Dawn Star that she is in fact Master Li's long lost daughter, and then again when it turns out the final phase of Master Li's plan to rescue himself and defeat the Emperor which his accomplices have been guiding you through is killing you.
- Not to mention that The reason you are the last spirit monk is because Sun Li killed all of them, except you, who he trained for use against his brother, the emperor
- In Suikoden V, you play as the prince of a large and powerful kingdom. The plot is kickstarted when the powerful Godwin-family seizes the castle with their private army, kills your parents, and forces you to flee into exile along with your faithful bodyguard, Georg, who was a close friend of your late father. Much, much later, you 'rescue' a former Queen's Knight who had been forced to work with the Godwins after they seized control of the palace, and she soon reveals that Georg was the one who killed the Queen. He might have had a reason, but it still seems like it would've been a good idea to let you know...
- Of course, you have the chance to find out beforehand: If you investigated Georg thoroughly in the second game (which happened, chronologically, after the fifth), it's revealed that he supposedly killed the queen of a foreign land. Also, it's fairly heavily foreshadowed in Suikoden V itself, to the point where it's not much of a surprise.
- The heroes just assumed he was innocent; Georg never claimed differently, nor made any effort to disprove it. Also, this trope is played more straight with the "rescued" Queens Knight rather then Georg, as she had only witnessed the end of that whole sorry affair. It's not until later when another Knight (who saw the whole thing) shows up that the full story is set reviled.
- BioShock uses this to explain its Arc Words.
- This is pretty much the entire plot of Metal Gear Solid 2: Sons of Liberty.
- In Fallout 3, the Lone Wanderer's father doesn't tell him that he wasn't born in Vault 101.
- A variation is done in Devil May Cry 3. Arkham tells Lady that he was possessed by "a demon named Vergil" when he murdered Kalina Ann, tricking her into going after Vergil to get revenge. Cue, "You forced him into this!" "Is that what you think? Foolish girl."
- Never try to keep a secret if you're an It's Walky! character. The Head Alien will pull this trope on you every time.
- In Inverloch, Achelon's family knows a secret he does not, and prefers to let him discover by himself that he is actually the elf he is looking for.
- Antimony in Gunnerkrigg Court is being kept in the dark about her parents. Granted, she isn't asking the faculty who presumably could help her; the one person she does ask isn't answering because he's a self-centered jerk.
- In Juathuur, Soveshei says this to Dejoru. Who lost his parents "in a storm at sea".
- In El Goonish Shive, Elliot learns about the other side of the story of Justin's outing. "She told *one person*."
- Harley Quinn found herself subjected to this trope in Batman: The Animated Series. With Batman trapped, she tries to defend the Joker... only to have Batman recite exactly the same Freudian Excuse backstory the Joker had told her - but with one detail changed. She realizes the story was a lie and breaks down. (It ultimately doesn't change her opinion of the Joker, but by that point she was already insane...)
- Winx Club has Bloom finding out about her royal roots (which is why she has her powers) from the Trix, even though Faragonda had at least suspected her roots earlier.
- Codename: Kids Next Door actually uses these words exactly, with Father telling Numbuh 2 that contrary to what 2 had been told, 2's father always finished last in tubing.
- The Simpsons uses this trope in one episode which had Marge initially being utterly terrified of flying in an airplane. During her time spent with a psychologist, it is eventually revealed that this fear all started when she was a young child. Her father told her all about the exciting job he had as an airline pilot, but one day she sneaks onto the plane where he's working and discovers, to her shock and dismay, that he is actually a mere flight attendant (or "steward", as they were called back in the day). The fact he had to wear the same uniform as the stewardesses didn't help.
Dr. Zweig: Yes, yes, it's all a rich tapestry.
- Marge also brings up memories of her grandmother accidentally poking her in the eye as a baby while playing airplane, a toy plane catching fire, and having a plane fire at her and her mother while looking at corn.
- In an alternate timeline of Danny Phantom, Maddie is convinced by her husband Vlad that her actual true love, Jack, hates her for the mistake that has been bestowed upon him—that is, being half ghost and thoroughly miserable about it—only to find out that Vlad had been lying to her to keep Jack out of the picture due to jealously. Jack was obviously still in love with her. Danny eventually fixed the mess.