A lot of times in life, lots of people jump to conclusions about certain kinds of things. After a little bit of misunderstanding, once a character finds out what's really going on, he will then proclaim rather blatantly that he knew it all along. This is something that a Large Ham, a Small Name, Big Ego, an Idiot Hero, a Know-Nothing Know-It-All, or a Miles Gloriosus is expected to do.
- After the first stage of the Chuunin exams in Naruto, Proctor Ibiki explains that there are two members of the test takers who served as cheating fodder for the others, which several shinobi noticed, but Naruto is not among them. However, once Ibiki explains this, Naruto acts as if he figured it out halfway through.
- In Pretty Cure All Stars DX 3, Cure Marine and Cure Rhythm start panicking when Cure White, Cure Egret, Cure Mint, Cure Aqua, and Cure Berry start taunting Freezer and Frozen. When it turns out that their taunting leads the two to freeze the water they were trapped around, Marine instantly declares that it was a great plan and she knew it all along. The others don't buy it.
- In the Donald Duck comic "The Old Castle's Secret", after the "ghost" is revealed to be a guy using invisibility spray, Donald tries to claim he knew it all along (rather than being terrified out of his wits while Huey, Dewey and Louie single-handedly solved the mystery themselves). His nephews are not amused.
- Played for laughs in this video where someone plays Kirby Super Star and is terrified of Waddle Dee. A bystanding Straight Man makes some rational observations on him, all dismissed by the player as "Lies!" The friend eventually tells the player how to get Kirby to properly attack (to which the player expresses amazement), and once Waddle Dee finally dies, the player exclaims, "It worked! I'm a genius!"
- A Goofy Movie: At the Neptune Inn, Pete pranks the Goofs by bursting into their room with a policeman act, and Goofy claims to have known it was him.
Goofy: You sure had him fooled, Pete.Max: Me? You jumped out of your skin!
- The Land Before Time: After Cera was cornered by a pack of Pachycephalosauruses that were scared off by a seemingly monstrous tar blob monster, she becomes afraid that the monster will get her too. However, the monster turns out to be Littlefoot and the others all covered with tar. Once Cera realizes this, she then proclaims that she knew all along that it was them, being the ego brat she is.
- In The Little Mermaid (1989), this was Scuttle's response after Sebastian tells him that Ariel had gotten legs (Scuttle knew that something was different about Ariel, but kept guessing right off the bat that it was something else).
- Austin Powers: In The Spy Who Shagged Me, Basil's response to learning that Vanessa was a fembot is to sadly say that they knew all along... before moving on and never bringing it up again.
- The Fugitive (1993): The U.S. Marshals are listening to the tape of Kimble's phone call to his lawyer. Several of them say they think that a sound on the tape is made by an elevated train, but Gerard disagrees and sarcastically abuses them. As they continue to analyze the tape they realize that Kimble was calling from Chicago near an elevated train line.
Gerard: I knew it was an elevated train.
- Harry Potter:
- In Harry Potter and the Chamber of Secrets, Professor Lockhart claims, after Professor Snape hits him with a disarming spell during a demonstration, to have known what Snape was going to do, and that if he wanted to block it he could have.
- When Harry and Ron are hiding in the teachers' room and someone suggests a remedy for the students' petrification, Lockhart is heard to mumble something along the lines of "Of course, it's what I've been saying all along."
- C-3PO says the line verbatim in The Empire Strikes Back, claiming he knew all along that Lando Calrissian was really on their side. Of course, this seems more like wishful thinking that just happened to be correct, since 3PO was already having a pretty bad day what with being dismembered and carried around on Chewie's back like a bookbag, and he really wanted to catch some kind of break.
- In Stage Door, Anthony Powell is a nervous wreck on opening night because Terry Randall, the actress he picked for the lead part of the show he's producing, has been terrible during rehearsals, and the only reason he cast her in the first place was because his mysterious benefactor insisted he cast her. When she ends up giving a brilliant performance opening night - due to circumstances he's entirely unaware of - Powell acts not only as if he knew Terry was going to be good all along, he also acts as if he always knew the benefactor was in fact Terry's father (who, ironically enough, was hoping she'd fail so she'd quit acting).
- Lynch, Bud Fox's boss in Wall Street, tells him "The minute I laid eyes on you I knew you had what it took," when Bud's star is rising. When Bud is arrested, Lynch has his own personal retcon, saying, "The minute I laid eyes on you I knew you were no good."
- Amelia Peabody and her husband Emerson both like to claim to be better at detective work than they actually are:
- In The Curse of the Pharaohs, most of the "deductions" Emerson claims to have made were actually things he had no idea about until the killer confessed.
- In The Deeds of the Disturber, Amelia gives The Summation to their assembled friends, explaining why one person and one person only could be the mastermind behind the murders. When she and Emerson are in bed together later, however, they both confess that they had both suspected the wrong person right up until The Reveal.
- In Cards on the Table, when Hercule Poirot reveals the identity of the murderer, Ariadne Oliver - who by this point has accused just about everyone - declares that she'd always said they'd done it.
- In the Sesame Street book, The Monster at the End of This Book, Grover is trying to stop the reader from reaching the end of the book because he doesn't want to get to the monster, and tries various methods to prevent it from happening, none of which works. In the end, he turns out to be the monster in question. He tries to play it off, admonishing the reader for being scared, then walks away feeling embarrassed.
- Buffy the Vampire Slayer: Willow, on learning of Xander and Cordy's makeouts.
Willow: I knew it! Well, not in the sense that I actually knew anything, but you two were arguing way too much!
- Doctor Who: Most certainly NOT Played for Laughs in "Midnight". After claiming loudly and vocally that the Doctor was possessed by the entity and that he should be thrown out of the airlock, the mother weakly claims that she knew that it wasn't him all along. She wisely shuts up after the Doctor gives her a Death Glare.
- Played with in The Flash (2014), when Barry Allen told Joe West and his daughter Iris about his ordeal on Earth 2. At one point he revealed that Iris on Earth 2 was a police officer.
Iris West: Told you I would have made a great cop!
Joe West: Don't get any ideas.
- In Rosencrantz and Guildenstern Are Dead, Rosencrantz thinks he hears music, but decides he must be imagining it. Guildenstern then tells an allegorical story about a man who sees a unicorn but doesn't believe it until other people also say they can see it (and the more people see it, the less fantastic they find it). By the time he's finished the story, Rosencrantz has decided "I knew all along it was a band." Guildenstern sarcastically echoes "He knew all along it was a band."
- In Far Cry 3, Player Character Jason Brody must go undercover as Foster, one of Hoyt Volker's privateers. This includes torturing his own brother Riley to maintain his cover. Then in the evening, Jason and his ally Sam go to play poker with Hoyt, planning an Assassination Attempt on Mr. Volker. Instead, Hoyt stabs Sam to death at the table and smugly tells Jason that he already worked out who Jason was a lot earlier, which means Jason's attempt at infiltrating his men was All for Nothing except to satisfy Hoyt's sadism.
- In Star Wars: The Old Republic, at the end of the Bounty Hunter's Story Quest on Balmora, the Hunter can claim that they knew all along that their employer's slave was actually a rival hunter in disguise. Their companion Mako doesn't sound too convinced.
- Woofer on Clue Club always brags to Wimper of how he knew who the mystery's culprit was and his modus operandi.
- Parodied in Freakazoid!. Freakazoid is forced to ignore his arch-nemesis, the Lobe, as he wreaks havoc all over the city, as part of the Lobe's request on Freakazoid's birthday (long story). Eventually, Freakazoid reads one very important detail and shouts, "I KNEW IT!" But a caption appears on the screen saying "NO, HE DIDN'T."
- Phineas and Ferb: In "Canderemy", Candace makes a promise to spend the day out with Stacy and not even mention Jeremy. Unfortunately, she also has to hide the fact she and Jeremy (who's sound asleep) have literally been joined at the hip, thanks to a stray shot from Dr. Doofenshmirtz's Combine-Inator. Just as the two get separated and Jeremy wakes up and leaves, Stacy reveals that she knew about the ruse the whole time.
Stacy: By the way, the best part was when you used him as a table. Busted!
- In the Scooby-Doo, Where Are You! episode "Never Ape an Ape Man", Shaggy gets "grabbed" by a stuffed ape. Upon being told this, he says, "Well, I certainly hope you don't think he had me fooled for a minute. I knew it all the time." Scooby sees right through him.
- Shaggy actually says this a lot in order to not look like a coward, even though they already know he is.
- In the Teen Titans Go! episode "Parasite", Robin is convinced that the titular parasite that Starfire wants to keep as a pet is an evil creature that will turn out to be some monster they'll have to fight at the edge of the universe. He repeatedly voices this fact as it starts to win everyone over, but eventually relents and decides that he's in the wrong... only for the parasite to then morph into said giant monster that summons them to a battle at the edge of the universe. Cue gloating.