Bluffing the Imposter in Anime and Manga.
- A rare case of this happening to the protagonist occurs in Arisa. Tsubasa is disguised as her titular (comatose) twin sister in an attempt to figure out the true identity of "the King", a figure causing all sorts of bullying, manipulation and general chaos at Arisa's school. At one point, she receives a message from someone she strongly suspects to be the King, telling her to meet them at the place Arisa's boyfriend took her on her birthday. Tsubasa can't find that detail in Arisa's letters, so she feigns memory loss from a stay in the hospital to get the boyfriend to tell her. She was doomed from the start, though, since Arisa's boyfriend is the King and has known about the switch the entire time.
- Both in Case Closed and Magic Kaito note has a flashback episode which Kaitou Kid encounters Shinchi Kudo. Kaitou Kid disguised himself as a regular police officer to try and steal the clocktower. The police department know Kaitou Kid is a master of disguise so they ask everyone their name and badge number. When Kaitou Kid is questioned, he gives the person's name and badge number, then the officer ask what their ID number is, which Kaitou Kid gives correctly, and that tips officers that he is Kaitou Kid. Shinichi told the officers to ask for the ID number as most people do not know their ID numbers and figured Kaitou Kid would answer the question.
- In Descendants of Darkness, Hisoka suspects that Tsuzuki is possessed by a demon and tells him, as usual, to bring something to eat for their boss Chief Konoe. He "reminds" Tsuzuki that Konoe hates sweets, and when Tsuzuki falls for it, he knows it's an impostor. (Konoe has a notorious Sweet Tooth.)
- In Digimon Fusion, episode 39, Kiriha suddenly remembers to return a Digimemory he borrowed from Taiki, and Taiki agrees. Except that the borrowing never happened, and Kiriha hands over a small explosive device that ruins Splashmon's impersonation of Taiki.
- Love of Fresh Pretty Cure! bluffs an impostor of her mother by switching her and Setsuna's presents and thanking her for the wrong one.
- In From Eroica with Love, Major Eberbach tests if a guide who called him is a KGB spy by asking her about a fictitious aunt. When the guide gets confused, he concludes she's no spy, because a spy would've pretended to know the woman.
- Fullmetal Alchemist: Riza Hawkeye and Roy Mustang are hunting down the shapeshifting Envy and get separated; when they meet up again, they exchange a few words, then start off looking for Envy... until Hawkeye puts her gun to Mustang's head. It looks like Hawkeye might actually be Envy, until...Mustang: What are you doing, Lieutenant? Don't you know who your gun's pointed at?
Riza: Who? Don't make me laugh. When we're alone the Colonel always calls me by my first name, Riza.
Envy: Grk! (dives away, transforming back into Envy) So you two are that close, are you?
Riza: I Lied. *BANG* But thanks for falling for it. Now you can do me the favor of dying. - In Guyver, protagonist Sho is handcuffed to love interest Mizuki so he can't bio-boost without blasting the broad to bloody bits. Hearing half a warning that she might not be who she appears to be, Sho laments that this had to happen right after Mizuki's birthday. She agrees, and her cover is blown because Sho knows her birthday is later in the year.
- JoJo's Bizarre Adventure: Stardust Crusaders:
- During an attempt to find an enemy Stand user, Jotaro claims that Stand users have blood vessels on their nose that stand out when they inhale cigarette smoke. All of his allies reach for their noses... as does the captain of the ship they're on. Then Jotaro adds that he was bluffing, and his suspect drops the innocent act.
Polnareff: You can't be serious, Jotaro!
Jotaro: You're right. I lied. But it looks like someone fell for it.
Captain Tennile: Ahh!- This happens again later to Oingo who uses his Stand to be disguised as Jotaro himself, albeit unintentionally. His plan to kill Jotaro goes horribly awry when Jotaro's friends all force him into their car and, because they're bored, repeatedly request "Jotaro" to perform various stunts of increasing danger (such as holding multiple lit cigarettes inside his mouth), each time saying that Jotaro is good at this sort of thing. Oingo pulls them all off and so Jotaro's friends never once suspect he's a fake, but Oingo gets so nervous that he decides it's not worth the risk of self-mutilation and, claiming he needs to take a dump, escapes from the car as far as he can run.
- Done heartbreakingly in Karin (with a bottle of Tabasco sauce) towards the end of the manga, to determine if the title character's sister has matured to the point where scheduling differences now leave her without any daywalking family. Adult vampires, you see, have no sense of taste.
- Happens in K-On!: Ui has disguised herself, rather convincingly as Yui until she slips polite speech which starts to undo her cover. She tries to deny it but Azusa demands Ui call her by her nickname.
- In Love Hina, Keitaro lies about being a student at Tokyo U, so Naru asks him about the miso-boiled lobster they serve in the cafeteria. Keitaro babbles on for a bit about how it's his favourite food that he can't start the day without, before Naru tells him that there is no such thing as a miso-boiled lobster.
- Naruto:
- Sasuke came up with a very long and convoluted "password" for his two teammates to memorize in case they ever needed confirmation of one another's identity. Naruto leaves to go to the bathroom, and when he comes back, Sasuke asks him to code in. Naruto repeats it back perfectly... and Sasuke decks the imposter, declaring that the real Naruto would never have been able to remember something that long.
- Later, the Mizukage does this quite expertly, although her victim is not an impostor, but under control. Ao, possessed by one of Danzo's men, encounters the Mizukage and Chojuro, apologizing to the latter for getting into a position in which he needed help, then asks the Mizukage to remove the seal on his eye. She then points out that Ao would not apologize to Chojuro, and he'd know the sealing tag could not be removed, then punches him when he calls her an old hag, thus restoring Ao to normal.
- Naturally, Naruto is too stupid to pull one of these himself. In one filler arc, he, Hinata and Kiba have to deal with impostors copying their every facet. So naturally when trying to identify the real Hinata, rather than asking a baited question like, "Hey, Hinata, how did you defeat Neji during the Chuunin exams?" he inverts the trope, asking, "What is the name of Hinata's father?" — a question any good imposter would study beforehand, but one that Naruto himself didn't know the answer to, making it utterly useless even if the imposter didn't know!
- Sakura pulls one of these off against Zetsu, who was impersonating Neji during the current world war. Or rather, Zetsu does it to himself. When Sakura mentions that Tonton (Tsunade's pig) is being looked at for a twisted leg, Zetsu!Neji says that it's better to have injured her leg than her hand, then asks if Tonton can still weave signs. Sakura says yes, but then when Zetsu!Neji comes closer, she pounds him into the ground and tells him that Tonton's a pig.
- This is actually quite a clever application by the writers considering that the Zetsus seem to learn a fair amount about the people they impersonate. Neji's team mate is Tenten. It's not such a stretch to think that Zetsu was simply trying to be too clever.
- Episode 333: The imposter shows up in front of the real Naruto Uzumaki and declares that he is Naruto Uzumaki. Until Naruto said that he was the real one and the imposter got curbstomped
- In Obsolete, during a demonstration of their uparmored Exoframes to Rei Miyajima, Captain Wangchuk of the Indian Army Special Warfare Brigade Ladakh Scouts demonstrates a "traditional Indian exercise" while operating an Exoframe. At the end of the episode, Wangchuk reveals to a subordinate that the exercise was actually a common Japanese calisthenic routine, and the fact that the Miyajima didn't immediately react or recognize it confirmed Wangchuk's suspicions that Miyajima was not from Japan, much less seconded by the Japanese Ground Self-Defense Force as he claimed to be.
