Tattle Tail

His poker tail was a poker fail.

Calvin: Look, stop being such a baby and help me push the car into the driveway. We'll move it 10 feet. What could possibly go wrong?!
Hobbes: Whenever you ask that, my tail gets all bushy.

— Calvin and Hobbes

Tails can reveal quite a lot about the tailbearer. Maybe the owner of the tail isn't used to having one, maybe they have no idea what's going on behind their back, or perhaps they simply have no control over such an emotive appendage. It wags when happy, tucks between the legs when scared, stands up straight when angry... tails just seem to have minds of their own.

Because of this, the individual probably won't be that great at gambling. It may be even more problematic if they need to lie or bluff their way out of a situation. And it might get especially awkward if they're trying to play it cool around someone they can't stand or have a secret crush on. Whatever the case, the tail has little sense of restraint or shame, often to the dismay and embarrassment of the one who has it. After all, Nobody Likes a Tattletale.

This can be seen as the opposite of a prehensile tail where the possessor can consciously control its movements, although both tropes can simultaneously apply in certain cases.

Not to be confused with Tipped Off by the Tail, where a tail merely exposes a disguise rather than expresses a character's feelings.

Compare to the cousin tropes Expressive Ears and Expressive Hair. Often overlaps with The Tell.

Not to be confused with the video game Tattletail.

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Examples:

Anime & Manga

• Beastars: After meeting with Haru a few times, Legoshi has trouble understanding his feelings whenever he thinks of her. It's only after he notices his tail wagging that he realizes she makes him happy. Later on, when Legoshi is cornered by the Shishigumi, they are confused as to why Legoshi would wag his tail, especially in a life-and-death situation. Deep down, Legoshi was merely relieved to see Louis was okay, but not wanting to give away their relationship he desperately tried to keep his tail still, to no avail.
• The Rising of the Shield Hero: The Little Bit Beastly raccoon demi-human Raphtalia often wags her tail when trying to deny wanting or needing something. I.e. early on in the series when Naofumi notices Raphtalia watching other children playing with a ball, he asks if she wants one. Despite Raphtalia emphatically denying her want for one, her tail indicates quite the opposite.
• Spice and Wolf: Horo, being a sapient wolf in human guise with wolf ears and tail, can give away her moods with her tail. When entering a city, for example, Lawrence becomes aware of Horo's tail wagging when she sees and smells apples at a stall along the main road. And her tail can swish angrily when she's in a foul mood, as well. She also wags her tail in "Wolf and the Amber Melancholy" when she thinks about Lawrence doting on her while she's sick. And it stops when she sees that Lawrence brought Nora Arendt to check on her, as Nora is a romantic rival as far as Horo is concerned.
• Tokyo Mew Mew: The Mew Mews have to fight giant insects in one story, and Mew Zakuro's tail fur gets puffed up when she's around them, indicating that she's afraid of them and insects in general.

Comic Strips

• Calvin and Hobbes: Hobbes' tail gets pretty emotionally expressive at times, such as when he and Calvin are playing poker. Calvin sees Hobbes' tail flick excitedly hinting that he got a really good hand. After Calvin promptly folds, Hobbes asks if he's cheating, indicating that he has no idea what's going on behind his back.

Fan Works

• RWBY fanfiction Knight of Salem: Beacon's resident eccentric doctor Tsune's eagerness to test the "perpetual organ donor" potential applications of Salem's magic on Ironwood are completely professional. Honest. There's no reason why her Faunus tail is wagging eagerly when she assures you of that.
• Helluva Boss fanfiction Owl's Hell That Ends Well: At one point, Loona's tail waving gives away her enthusiasm to do something to her present company when she's trying to restrain it, to her annoyance.

Films — Animated

• The Bad Guys: Wolf inadvertently ends up helping an old lady he was trying to rob who in turn praises him for being "such a good boy". Having been called good for the first time in his life, Wolf's tail wags eagerly, even as he frantically tries getting it to stop. The rest of the "bad guys" also experience wagging later on, although Snake is the only one with a wagging tail (Shark and Piranha wag their fins and Tarantula wags her abdomen).
• Ferdinand: Despite Paco the dog stating that it's weird for a bull and dog to be considered brothers, Ferdinand points out that his tail wags whenever he calls Paco "brother", despite Paco's attempts to get it to stop.

Literature

• Diary of a Wimpy Kid: In "Double Down", Greg has a dream where he's grown a lizard-like tail. Though initially he finds the tail useful, he doesn't like how it wags whenever he's excited since everyone can tell. An illustration demonstrates this when his mom asks if he likes a cute girl, and despite saying no, Greg can't keep his tail from wagging.

Puppet Shows

• Fraggle Rock: During the Trash Heap's upbeat song, "Go with the Flow", Boober groans, "I hate this." Red can tell this is a lie because Boober's tail is wagging.
  Boober: [to his tail] Stop it! Stop it!

Video Games

• Fire Emblem Fates: Whenever Keaton the wolfskin man acts like a Tsundere, he often claims he doesn't care about something, only for his wagging tail to give it away. In his introduction alone, he claims not to like being recruited into Corrin's team, but then his tail starts wagging, much to his embarrassment.
• Genshin Impact: whenever the nekomata Kirara has to lie, her two tails twitch uncontrollably. The same happens when she gets nervous.

Web Animation

• In RWBY, Marrow Amin is a Faunus whose animal trait is a dog's tail. When he is formally introduced to the protagonists, his attempts to play it cool are ruined by his tail's eager wagging, showing how happy he is to meet them. RWBY: Amity Arena states that this trait always makes him fail his interrogation training.

Webcomics

• Awoo: In one strip, Kevin gives Pink Wolf a gift. Being tough, Pink Wolf wants to pretend to hate it but is caught because their tail is wagging.
• Freefall: Subverted. Florence, an uplifted wolf, is prone to tail wags when excited. However one of the bonus comics◊ shows her intentionally wagging during a poker game as a bluff.
• Ozy and Millie: It's mentioned frequently that the tails of the fox characters show their emotions. Specific cases include Ozy and Ms. Mudd.

Western Animation

• Bluey: While the anthropomorphic dog characters throughout the show have moments where their tails wag subconsciously, indicating joy, it is particularly prominent as part of an Aesop in "Duck Cake". Bingo picks a duck-shaped cake for her birthday because the picture "made my tail wag", and asks her mother how animals without tails know when they're happy. Later in the episode, Bluey's tail starts wagging after her father praises her for doing something helpful without being asked or bribed as she had before. Bluey is at first surprised by this but quickly realizes helping her loved ones for the sake of it makes her happy. This makes her keep doing it, showing her character development.
• Kleo the Misfit Unicorn has an episode called "The Tell-Tale Tail". In it, a monkey named Conrad wins a swinging competition by cheating, and his tail keeps trying to remove the winner's crown from his head.

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