Oh Crap/Fan Works

""Okay...natural selection; the dumb ones are all dead, so the survivors are a little bit smarter!""
 * In Forward's first "episode" there's the scene where Adelei Niska realizes that he's in the same room as an enraged Jayne Cobb (who he's been torturing periodically for the last several chapters), that Jayne managed to cut himself free, all his guards are dead, and Jayne wants fingers.
 * In ''Harry Potter and The Methods of Rationality chapter 6 Harry has this memorable quote right after his realization, he even literally thinks "aw crap" :
 * Used in Seduction when Sarakshi Ishin (who's agreed to let Magnificent Bastard Tora Igarashi take off her shirt if she loses to him), realizes Tora knows the person he just defeated isn't a guy, but her dressed as one.
 * In the Star Trek/Babylon 5 fan-made spoof film Star Wreck: In the Pirkinning, this happens more often than would be reasonable to recount here.
 * A common reaction to a great many things in Tiberium Wars. For example, GDI troops have a spazzing panic attack whenever they encounter the Black Hand (for good reason), and the Nod troops have one when they encounter an entire division of Mammoth Tanks.
 * DC Nation: Happened to Terra twice during the final brawl in "Strangers." Dark Angel's spell had swapped out several Titans with evil counterparts, with those under the spell feeling for the villain they had felt for the person they got swapped for. Terra got swapped out with Fauna, Beast Boy's current girlfriend. In the middle of the fight, the spell is broken, and Gar realizes that Terra not only tricked him for a second time, but just tried to kill his girlfriend. She still thinks he's the Joke Character he was at fifteen, only to realize he's Taken A Level In Badass since then. And just when Terra manages to incapacitate him? That's when Fauna hits her limit and comes within inches of decapitating Terra!
 * There are tons of examples in An Entry with a Bang!, starting with the initial pirate raid in 2005, when people on Earth realize that they're getting visited by what they thought was a purely fictional universe.
 * The Inner Sphere rediscovering the value of the TAG (Target Acquisition Gear) warning light, courtesy of Earth's laser guided munitions, also qualifies. Not that most of them survive the lesson, mind you...
 * The pirates get one when Earth starts firing nukes at their fleet.
 * Freemans Mind, where Gordon Freeman finds out the hard way that the soldiers pursuing him in Black Mesa are learning from their mistakes...


 * Used as a Precision F-Strike in Kira Is Justice, when Justin realizes L Near figures out Kira is in Chicago. He literally thinks, "Oh, crap."
 * Power Rangers GPX is filled with these expressions. Most of them happen when a character realizes they're in for a pounding, like in  There's also
 * Part 2 starts out with the Rangers who think they outsmarted the Zordonians after moving, realize they've been found by the Zordonians--by watching their attack on the news.
 * The Galaxy Rangers fanfic Chrysalis has a Mass Oh Crap from both the Rangers and the Mooks when Zach flips the hell out due to one Mind Rape too many from Queen, and traps them both in the Psychocrypt device. Then, Doc reads that, somehow, Zach has triggered his implant...
 * In Kamen Rider Kage, General Kyo Takeshi realizes that his genetically engineered Mix and Match Critter that he can no longer control survived it's failsafe. The only description given for his reaction is "Oh Crap".
 * In the Fruits Basket fanfic "Eyes of The Cat", Akito has an Oh Crap moment when
 * The Touhou fan comic "Let's Play Resident Evil" has quite a few of these moments, most of them involving Ran.
 * "And only too late did Celestia realize the corruption in her own court..."
 * Later,
 * The READERS of Imperfect Metamorphosis get one when they realise that The Fourth Wall Will Not Protect You from Yuuka anymore. Here's the moment of realisation:

"Mr. Incredible: My God... WHAT HAVE THEY DONE?!"
 * Tamers Forever Series: Any time Chaosgallantmon or Daemon appear, expect this reaction.
 * Hunting the Unicorn: When David realizes that  his expression is this. As are the Dalton staff's expressions when they find out.
 * The Warblers are actually pretty calm when  Until Kurt finds out, in which a string of "Oh Crap" text-messages are unleashed.
 * Many people in With Strings Attached have these:
 * The cop in New Zork freaks out when Paul breaks the handcuffs that were supposed to have neutralized his Super Strength.
 * The Hunter stands in stunned amazement when John lifts the river.
 * has one when he realizes that Paul isn't mind-controlled after all.
 * There is a collective one amongst the Raleka and skahs wizards when Sapsa hits Paul with an enormous burst of flame, and Paul says, “That was lovely! Do it again!”
 * When Shag and Varx reveal to Jeft that they'd told the real Dalns gods what was going on. “Did you want gods pissed at you, Jeft?”
 * "Hello, brother."
 * And speaking of, it's almost a given for everyone to react in this way any time any Eldritch Abomination, such as, shows up.

"My name is, and I remember everything."
 * The reaction of the entire "Wargods" strike force and the player when Things go downhill from there.
 * The twisted My Little Pony Friendship Is Magic fanfic "Pattycakes" has a literal example. After spending the entire fic as a prisoner, with a badly derailed Fluttershy attempting to Mind Rape her into an infantile state, Rainbow Dash messes her diaper and is so terrified by the situation that her will breaks and she starts believing herself to be Fluttershy's baby (this was later retconned into being the effects of a mental regression drug Fluttershy created, since it generally takes more than an afternoon to totally shatter someone's will). Scootaloo gets a similar reaction to the same stimulus in one of the endings, after drinking something doped with an irreversible dose of the aforementioned drug.
 * Happens in chapter 8 of Ace Combat: The Equestrian War. When, Lightning Bolt, Derpy and Soarin' just stare at it, realizing they are screwed.
 * Ironic Echo: the griffins have the same reactions two chapters later when.
 * Through a Diamond Sky has a couple. A minor one is when the leader of the Iso colony is being rude and realizes that the visitor asking questions isn't Clu, but Flynn himself. The second, larger, one is when a Mook realizes that they just made the fatal error of trying to kill Tron.
 * Plenty of these abound within Streets of Rage Saga, but the crowning one (as of this writing) has to be during the epilogue of the fourth story in the series, The New Syndicate: The Syndicate has kidnapped and attempted to mind-wipe . It seems to have worked at first ...but they weren't counting on hearing anything contrary mere minutes later. So cue the man in charge turning pale when he hears this line:

"Hisao narrating: Oh fuck."
 * In the Katawa Shoujo fic Lilly Epilogue Family Matters, Hisao has this reaction after hearing that Lilly's family is coming to visit. To put things into perspective, in Lilly's good ending she, and Hisao thus fears they will not take her decision well, potentially forcing her to come home.