The Mind Is A Plaything Of The Body / Fan Works

• DC Nation: An unfortunate side-effect of Fauna's powers. Yes, she can partially shape-shift into most animals, as well as speak to and persuade animals to ally with her, but the harder she pushes her abilities, or the more wounded/angry she becomes in a battle situation, and the less she thinks like a human and the more she thinks like a beast. Worse, she remembers almost nothing of what happened during one of those "freak outs" afterward. As she told Changeling once, "You keep the mind of a man when you shift; I don't."
• In Deku 10, Izuku is very notably affected by whatever alien form he transforms into. As Bullfrag, he gains a notable sadistic streak and wants to do good by the Incursean empire.
• In the sequel of Child of the Storm, Harry and Carol discuss (in reference to Harry being sorely tempted to turn Jean's cheating boyfriend into a frog) the ban on forcibly transforming others into animals under the Laws of Magic, and the laws of the Wanded magical world, because of it has this kind of effect - namely, they essentially become the animal, if they spend too long as one, effectively killing the person. Temporary transformations, such as those induced by Fred and George's Canary Creams (which in any case don't seem to be totally inhuman transformations, since the person who undergoes it remains the same size) skirt the line, but are broadly fine.
• George in With Strings Attached. His ring allows him to transform into any animal he can imagine, but becoming that animal also causes him to gain the senses, instincts and tastes of that particular creature. A few times, he has to exert his own will to keep from doing something inappropriate, like eating something (or someone) he's not supposed to.
• This is a core theme of Becoming Ponies. The counterparts are all having their personality slowly overridden with that of their associated character, and some of them don't even realize it.
• Harry faces this problem in No Longer Human since (as the title indicates) he isn't fully human anymore but a hybrid of a phoenix, basilisk, and human. When Ginny comes to him crying that the attacks were her fault and that she was controlled by Riddle's diary, all Harry feels is annoyance that she's getting his shirt wet and anger that she "allowed" herself to be controlled.
• The Parselmouth of Gryffindor has two variations on this same trope:
  • In an unusual willing example, the Voluntary Shapeshifter Maximilian can (and does) alter parts of his brain to become better-suited to whatever he's doing, such as turning off the part of his brain that induces boredom if he's studying. Other characters are understandably creeped out by this.
  • When part of Lord Voldemort's soul is transferred into one of the Hogwarts statues, said Horcrux finds himself unable to harm anyone or leave the castle, because all of the statues, whether animated or not, are bewitched to be loyal to the Castle as one of their core values so that they may act as protectors of Hogwarts in cases of emergency.
• In Walk Through the Valley by Vathara, Hiko uses LEGO Genetics to transform himself into a kiryuu alterant, a felinoid alien from the planet Satoyama. Upon becoming half-man, half-kiryuu, he takes on the kiryuu's territorial instincts despite being a drifter who previously never stayed anywhere more than a year at a time (except for his stint on Satoyama). Within five years, he finds himself killing in an Unstoppable Rage just to protect his territory. Later, he finds himself with a dying eight-year-old escaped slave boy (Kenshin) and the only way to save him is an Emergency Transformation into a kiryuu alterant. Previously, Hiko had been a borderline Child Hater who wouldn't have bothered. Similarly, Kenshin was hostile to a friend who approached the cabin despite caring for her, until he was able to rationalize her as a member of his pack to get around it.
• Diaries of a Madman: Navarone struggles with this, being particularly vulnerable to pony pheromones whenever he's turned into a pegasus. When gender switched for a prolonged period of time, he also has trouble dealing with certain urges while female.
• This is a major theme in The Land Before Time fanfiction The Seven Hunters. Although Littlefoot and the other members of the gang retain their personalities after their transformation into carnivores, they slowly begin to suffer from a personality shift as time goes on. They even begin to enjoy their hunts despite the realities of what that entails.
• A variation of this features in the Supernatural/Sherlock fic "The Case of Identity Switch" when Dean Winchester and Sherlock Holmes swap bodies, as Dean finds himself making Sherlock-esque intuitive leaps that he would not normally be capable of on his own. Castiel attributes this to Sherlock's faster brain allowing Dean to make those kind of intellectual leaps, where Sherlock has to concentrate harder in Dean's body to make his usual deductions as Dean's brain isn't used to thinking that fast even if Sherlock's mind retains the accumulated knowledge that allows him to make most of his deductions.
• In As We Chase the Sun, spending the better part of fourteen years in the form of a wolf as an animagus has led to Bellatrix practically forgetting that she even was human originally, only able to recognise Sirius, Andromeda and Narcissa as family through scent and other primitive measures. However, this has the advantage of making her more willing to essentially reconcile with Sirius and Andromeda in particular, as her wolf-psyche focuses more on the obvious idea of them as "pack" without thinking about the more complex issues such as the circumstances that drove her to sever ties with them in particular.
• Features in the Farscape fic "In the Flesh", when Moya is attacked by a crew who have acquired the weapon that caused the crew to previously switch bodies ("Out of Their Minds"). While this attack initially appears to have only caused Aeyrn and Pilot to switch, the crew soon realise a more serious problem has occured as Chiana has swapped with Moya. As observed by Pilot, this not only explains Moya's "silence" since the switch as Chiana-in-Moya has basically shut down to protect herself from the scope of trying to understand a Leviathan body, but he also worries about the possibility of Moya causing harm to either her mind or Chiana's body trying to cope in a form so utterly unlike what she's used to.
• In the Pizza Tower fanfic i was a middle-aged weretoon, it's clear Peppino's transformation into a Zany Cartoon character has also affected his mind, as he briefly considers using a hammer to stop his wildly-pumping heart.
• Invoked in Lost in Camelot when Dyson recalls how he first met Lancelot, as he spent several weeks in his wolf-shape to escape his human guilt at the loss of his friend and his exile from his pack, as his wolf self didn't have to deal with his more complex emotions of guilt and grief.
• Discussed in "Morningstar Family Values" when Trixie asks if Sabrina could show her magic by turning Trixie into a frog. Sabrina explains that it wouldn't be worth it because Trixie's brain would become a frog's during that transformation, so she wouldn't be able to remember it and would retain some unwanted frog instincts for the next couple of days, such as trying to catch flies with her tongue.
• At least suggested to be the case in the Power Rangers Zeo fic "Memory Lapse", which reveals that Shawna, a close friend of the previous Yellow Ranger Aisha, was actually Aisha's girlfriend. When Aisha chose to stay in the past after her quest for the Zeo Crystal and send Tanya back to the present instead (as depicted in "Hogday Afternoon"), Billy speculates that this was because Aisha's younger body stopped her remembering Shawna with the same degree of emotional attachment that she would have felt as an adult.
• The Stargate SG-1 fic "A Dog's Life" features this in both directions. When Daniel's essence is temporarily displaced into a dog's body while a non-corporeal entity uses his body for a couple of months, he often has to deal with resisting his dog instincts, such as being disturbed when his dog body reacts to the presence of a female dog in heat. Later, when Daniel misses the planned deadline to regain his body, the alien returns to Earth on its own accord because Daniel's body had an innate morality that compelled it to come back, recognising that Daniel wasn't at fault for his absence (Daniel was unaware that months on the other planet were slightly shorter than on Earth and missed the meeting by a couple of days).
• In Consequences of Unoriginality, Emeris is a human who was turned into an alicorn. For this reason, though it disturbs him, he finds mares sexually attractive. Subverted when he is depowered, revealing that his body is actually a Cosmic Horror and his pony nature is a way of protecting his mind from being twisted by by that body, because Friendship is Magic
• In the Avengers fanfic That Darn Cat, Loki is transformed into a cat by Odin as punishment, and sent back to Earth with Thor. While he mostly retains his personality, sometimes that 'cat instinct' will override it — such as when he's confronted with Darcy's knitting and can't leave the yarn alone, or when someone scratches behind his ears. The fact that he can't fight the instinct just makes him even angrier over the whole situation.
• In the Discworld fic Hear Them Chatter On The Tide, a powerful anthropomorphic personality who has been lost to the world for at least a thousand years is transformed into a sort of animal. The long-lost virtue, specifically, is Bissonomy, transformed into a shoal of oysters by a jealous fellow god. This demiurge has human followers whose goal is to restore her to human shape and potency. The problem is that as the Goddess Cult of the Blue Oyster discover, Bissonomy has spent so long as an oyster that she has forgotten she is human.
• In the Pokémon fanfic Morphic, most of the kids' personalities are influenced somewhat by the Pokémon they were fused with. For instance, Peter often makes twitchy bird-like movements like a Taillow, and Will (a Meowth morph) displays a lot of cat-like mannerisms. Additionally, it's revealed late in the fic that all of them have varying degrees of battle lust, just like "actual" Pokémon.
• In the Oversaturated World, it's the entire conflict of a story. In What Shy Did On Her Summer Vacation. Fluttershy decides to spend her summer vacation as a tree. This slowly leads to her becoming more distant and less caring about human concerns until, at last, she stops moving and starts to fade from consciousness entirely. Mildly subverted, in that it's stated it was less her state as a tree that caused the shift and more an unforeseen circumstance of the spell cast to turn her into a tree.
• In Destiny is a Hazy Thing Daiki's worldview has been seriously warped as a result of spending the last ten million years as a human. Before that he was Yog-sothoth.
• After being made 22 for a night in Dodging Prison & Stealing Witches, Hermione no longer has the hormones that affected her thoughts so much but still remembers her very physical attraction to Harry.
• Loaded Bones: Yami Bakura notes that most of his proclivities come from Ryou's brain.
• Deserted Distractions: Yami Bakura laments that this is the reason he's attracted to Tea; since Ryou is his host and likes her, he does too.
• For Love of Magic: Harry theorizes that Tonks' increased aggressiveness and attraction to women (years prior she only had minor interest and she's now fully bisexual) is due to her granting herself male genitals with increasing frequency (as part of kinky sex games with Fleur) which is messing with her hormones.
• Mergers has this grow more and more prominent the more Pokemon DNA you have, with Brock losing the ability to speak like a human.
• This is implied in Chapter 24 of The Portal when Blizzard says to Static that he believes that their transformation from humans into dragons has changed the way they think as well as their physical bodies.
• Universe Falls: In "Monster Falls", Bill Cipher and Yellow Diamond's combined attack turns the people of Gravity Falls into various monsters like werewolves, ghosts, gorgons etc. and the turns the gems into corrupt forms. While the gems still maintain their personalities, albeit without the ability to properly communicate, as time progresses the GF citizens become more like their monster selves, Cervitaur Dipper becomes more skittish, Mermaid Mabel acts more like a fish, Gorgon Pacifica embraces her predatory instincts and so on.
• This short comic shows off the consequences of Ganon possessing Zelda in The Legend of Zelda: Twilight Princess.
• In My Little Pony: Totally Legit Recap, Twilight's sudden infatuation with a guy she barely knows is explained as her being in the hormonal body of a teenager in an (in the creator's opinion) Animesque world is affecting her so much, she has to consciously fight her desires not to just bone him on the spot. She fails.
• Equestrian Legends has Meadow: formerly a pony, now a dragon, and with powerful instincts.
• Discord's New Business: Some transformations provoke the trope.
  • As a draconequus, Fluttershy sees how Discord sees the world. And goes on a prank fest.
  • As an alicorn, while she stays a Cloud Cuckoo Lander, Princess Pinkie Pie is also more mature than she usually is.
  • As a changling queen, Starlight craves love and instinctively slips into the form Discord would love most of all. She later does the same thing with Twilight, initially impersonating Shining Armour, before regaining control. Then she sees Sunburst and completely gives in to her queen instincts.

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