If Only You Knew

A character says something that connects to a fact or event of which he's unaware, usually to someone who is in the know. A common variation of this is You Look Like You've Seen a Ghost.

Often shows up in supernatural settings with a Masquerade, but mundane versions can occur, such as the Arrogant Kung Fu Guy telling Sweet Polly Oliver she "fights like a girl".

Sometimes subverted in that the seemingly Genre Blind character turns out to be hinting that he does know the truth.

If none of the characters know about the secret, but find out later, it's Foreshadowing.

This is sometimes expressed as "You have no idea" or something along those lines.

Contrast Literal Metaphor, in which Character A means what he says literally, but Character B takes it as a figure of speech. See also Accidental Truth. Subtrope of Dramatic Irony.

Anime and Manga

 * In Puella Magi Madoka Magica, Kyousuke, who doesn't know about Magical Girls, says it would take magic or some kind of miracle to heal his paralysed hand.
 * Rin, from Ao No Exorcist, was harassed and called a demon as a child. Guess whose biological son he turns out to be?

Film
"George: You can't see him. You wouldn't want to. Bessie: I do want to. How can you say a thing like that? Why can't I see him? George: It's impossible. His work for the Navy is top-secret. Just be happy with his paycheck. Don't even mention his name to anyone. Bessie: There's something fishy about this. George: You said it!"
 * Daredevil has a scene where Elektra sarcastically asks Matt, "Are you blind?" She apologises profusely when he tells her that, yes, he is.
 * The song "I'll Make a Man Out of You" in Mulan has the line, "Did they send me daughters when I asked for sons?" The commander thinks he's turning boys into men, but of course, with Mulan the starting point is a bit different! Though ironically, she becomes much a more capable soldier than her comarades in arms.
 * Strange Days: When Lenny asks Mace whether she knows what it's like to love someone who doesn't love you back, she responds this way.
 * The Incredible Mr. Limpet: George Stickel is trying to explain to Bessie that her husband, Henry, is still alive, but can't tell her the truth: that Henry has turned into a fish.

Literature

 * In Tithe, Kaye's grandmother says during an argument, "You think that it's enough to want things. You think that if you just want and want then you're just going to magically get them." Kaye, who's just found out, doesn't know whether to wince or smirk at the word "magically".

Live Action TV
"Girl: Have you heard the latest rumour? Apparently a woman was drinking a coffee when an eyeball fell in it! Mac: *smiles* Impossible."
 * In Heroes, Matt Parkman can read minds. His wife, Janice, who doesn't know, tells him, "It's like you're in my head!"
 * Similarly, in Supernatural, a woman is talking to Sam about her baby, Rosie. She says, "It's almost like she can read my mind." Since Rosie is one of the Special Children, she presumably can.
 * Comes up a lot in Slings and Arrows. One notable scene is in Season 3, when Geoffrey's therapist places an empty chair before him and tells him to envision Oliver sitting there and to talk to him. When Geoffrey opens his eyes, Oliver's ghost IS there (audible and visible only to Geoffrey) and they proceed to have a screaming argument, while the therapist marvels at Geoffrey's ability to engage in the therapeutic exercise.
 * One episode of CSI New York opens with Mac and Stella talking about someone from a previous case who Mac's worried about when an eyeball falls in Stella's coffee . At the end of the episode, Mac's speaking to said person;


 * In Arrested Development, this is done several times with Buster and Oscar Bluth, who is secretly Buster's real father.
 * Dexter is very fond of this. Characters often unintentionally say things that seem to be hinting at Dexter's dark nature, of which they are completely ignorant.

Web Comics
"Jason: "Lately I've been seeing a couple of weird-looking guys in goofy clothes wandering around, although I haven't seen them in a while. There've even been rumors that people spotted demons lurking around the inn a few days ago. Crazy stuff, huh Snake?"
 * In Slightly Damned:

Rhea : "You don't know the half of it, J.""

Western Animation

 * In Teen Titans, in the episode "Homecoming, Part 1", the Titans meet the Doom Patrol. The Doom Patrol expresses skepticism about the competency of the Titans to combat the Brotherhood of Evil, saying something along the lines of "We've been fighting this great evil our whole lives. What have you done?" One of the Titans--having just come from defeating a trans-dimensional demon who pretty much destroyed the world by showing up--responds, "You have no idea."