Organ Autonomy

"For the love of gods, watch where I point those swords!"

Zim: At this very moment I'm inside a microscopic submersible somewhere in your disgusting belly, attached to your arm control nerve!
Dib: Arm control nerve?
Zim: Yes.
Dib: In... my... belly?
Zim: Yes!
Dib: Humans don't have arm control nerves.
Zim: Do not question me! I control your arms!

—Invader Zim

This trope is for when parts of the body have "minds of their own" and will control or influence the brain of whoever they're attached to. Typically happens when said limbs aren't normally a part of the body, as happens to a Frankenstein's Monster or Shapeshifter Mashups.

When this happens but only the body part is shown, it's an Independent Limb. Related to Animate Body Parts. A supertrope of Evil Hand.

When a physical part other than the brain (usually the heart or liver) is the source of a person's emotions, see Cardiovascular Love.

Examples of Organ Autonomy include:

Advertising

Many commercials have the stomach "advising" to the brain what it wants to eat.
There's the Ball Park Franks commercials, which have the stomach spontaneously sprouting an arm and force-feeding the mouth.
The Nightmare Fuel Nike adverts, with an oversized beer gut chasing a guy down the street; "Belly's gonna get ya!".
There's this award-winning Alka-Seltzer commercial from 1967 (with Gene Wilder as The Stomach!)
Froot Loops: "Follow Your Nose!"
There are the Puffs facial tissue commercials:
- In one, a (CGI) child's sore nose flees around to the back of its head, to avoid being assaulted by an ordinary un-lotion-impregnated tissue.
- In another, the nose also turns into sort of a pipe, which you really wouldn't want happening to your nose.
- And in yet another commercial, a little girl brings Puffs tissues to her class, and all the other childrens' noses fly of their faces and go to hers.
Nightmare Fuel abounds in a California Milk Advisory Board that depicts a woman's skeleton shucking off the rest of her flesh in order to gulp down some of the calcium-rich fluid. The husband is oblivious as he watches t.v. in the other room, the skeleton retains the woman's voice... and the remaining flesh, left on the floor like a full-body sweatsuit, rolls its eyes as the skeleton keeps talking.
This surreal Old Spice commercial has the spokesman's abdominal muscles chime in on a sales pitch, and his right bicep grows an entire new arm in order to blame his left bicep.
Just-Eat is a restaurant food delivery service. Their ads feature a red blobby character named Belly and a little scheming yellow blob named Brain. The slogan is "Belly says takeout - Brain says Just-Eat!" The characters are clearly supposed to represent body parts although they are never depicted inside a body. Belly sits there and drools while Brain reads the Just-Eat menu.
This Nightmare Fuel Australian beer ad in which a man's tongue goes in search of beer while he is sleeping.
Hilariously |done here in a Claymation commercial for Tang, with too mouths who can't wait for the rest of their faces wake up.

Anime and Manga

Yu-Gi-Oh!: When Bakura is first introduced in the manga, Yami Yugi is playing a tabletop RPG against Yami Bakura. In the game, the Yugi party manages to sever the Big Bad's hand, and as a result, the real Bakura manages to re-take control of that hand of his body and is subverting his dark side's plans, a literal instance of the right hand not knowing what the left hand is doing. Yami Bakura eventually catches on and gets it out of the way by impaling it... but tips off the group as to his identity in the process.
The basic premise of Hell Teacher Nube is that Meisuke Nueno, a.k.a. Nube, has sealed an Oni as his left hand. He typically uses it as a regular hand (if ultra-powered when released,) but by the end of the manga he and the oni have become allies in a symbiotic relationship, and Baki (the oni) is free to do whatever he likes as Nube's hand.
Despite being attached to/having replaced Seiji's right hand, Midori from Midori Days has complete autonomy and freedom of movement. If she wants to go somewhere, she will, often dragging an unwilling Seiji behind her.
Vampire Hunter D has arguments with his own left hand—long ones, because the hand only ever shuts up around outsiders. It does, however, save his life on occasion—when you're in a high-risk profession like vampire hunting, it helps to have a hand that can give you CPR by itself.
In Umineko no Naku Koro ni's fourth arc, you get to see exactly what happens when someone tries to lie in red text when Battler tries to do so (not that he realizes that it's a lie at the time). The red background disappears, and Battler's arm reflexively reaches up to quasi-strangle him.
Parasyte has this. Basically, the main character's arm gets possessed by an alien parasite of a race that usually gets into the brain and takes over the whole body. Now they're a duo.
Zommari Leroux, the Eighth Espada from Bleach, can take control of objects or other people's body parts.
A hermaphrodite character in Hot Tails gets yelled at by her guy-parts when she tries to live a celibate life. When she objects, she's molested by her own penis until she gives into his(?) demands.
Happens in the third Inuyasha movie: A demonic sword takes control of Inuyasha's arm by burrowing tentacles into it and pumping him full of demonic energy. It tries to force him to slaughter a village, but he temporarily disrupts its control by biting his own arm and holding on with his teeth while Miroku saves everybody.

Fan Works

In one Stargate SG-1 fanfic, Dr. Daniel Jackson has a series of bizarre conversations with various body parts as a result of a caffeine overdose and nervous breakdown.
Harry has conversations with his brain when trying to escape from Azkaban in Harry Potter and the Methods of Rationality.
Melanie C's left arm comes to live for a brief moment to give the narrator a high five after dealing with Monty in Case of the Missing Technology. This creeps out the narrator for a moment.

Film

Spaceballs has Barf blaming his tail for trying to feel up a waitress's skirt—though his snickering afterwards suggests he was just lying.
This is a common horror movie trope. For example, Ash is forced to sever his possessed right hand in Evil Dead 2.
Idle Hands is basically the possessed hand scene from Evil Dead 2 blown up into an entire movie.
The little-known 1977 film Chatterbox is about a woman with a talking (and singing) vagina!
- There is at least one other movie with an almost identical premise as well as another that is similar, but is due to the vagina being possessed.
Soul Vengeance (aka Welcome Home Brother Charles) has a black man, experimented on during his term in prison, who takes vengeance on the people who put him there by strangling them with his giant prehensile penis.
In Peter Sellers' Dr. Strangelove; or, How I Learned to Stop Worrying and Love the Bomb, one of Dr. Strangelove's hands has a mind of his own, down to attempting to strangle him, and snapping off Nazi salutes.
Guess which organ has a mind of it's own in a movie called Pervert! The homicidal maniac turns out to be James' voodoo-enchanted penis.
Osmosis Jones, which is about several animated anthropomorphic microbes living inside a live-action man.

Literature

This explicitly exists as a fundamental law of reality in the Discworld series. Of course, in a world where the Law of Narrative Causality is also a fundamental law, it's hardly incongruous. In Pyramids, the mummified King Teppicymon XXVII awakens as an undead, but can't see. He fumbles his way to the canopic jar that contains his eyes, so he can return them to their proper place; through the disembodied eyeballs, he sees his own hand reach into the jar to collect them.
In one of Aesop's Fables, the members of the body refuse to help the belly. The body is dissatisfied with "King Stomach's" rule, so they overthrow him and try to decide who is most important and thus worthy to be king. Tongue nominates himself but is laughed off the floor; the debate continues without recess until a lack of rest and nourishment has everyone telling someone else to do the job since they're to tired to do it. They eventually work out that maybe King Stomach wasn't such a bad ruler and put him back in power, and go make soup so as to be not dying. Then the story derails and the body parts aren't metaphorical parts of everyone but the bits of one specific guy. This man hears that if he can collect the milk of a lion, the only cure for the disease from which the king's beautiful daughter suffers, he gets to marry her; in typical folk hero fashion, he does so by cunning and resourcefulness. Just as he is presenting the king with the milk, Tongue, still bitter about being called worthless, makes the man say it's the wrong kind of milk. The king gets angry, and nearly has the man killed, but the other body parts relent and agree to respect Tongue a little more, and Tongue corrects the mistake. Guy marries princess, happy ending, hooray.
There's a parody version of Aesop's fable, where the organs argue over which one is the king of the body, and they all seems to hate the anus because "he's an asshole", so the anus decides to clog up to "stop being an asshole" and the body gets gradually sick from constipation, then the organs apologize to the anus, which decides to work correctly (="be an asshole") again, the body recovers and the organs decide that the anus is the real king of the body. And this explains why in any organization or committee it's always the asshole who is in charge.
In William S. Burroughs' Naked Lunch, Dr. Benway tells the story of 'the man who taught his asshole to talk'. Bad idea.
There was a story in a magazine of Short Science-Fiction stories featuring an antagonist who was a member of a species whose reproductive organs became active and self-motivating after death. He happened to have a genetic flaw that caused his to activate early, resulting in constant arguments with his gonads, which were usually concerned with finding a female and spreading his seed. Eventually, they leave him in disgust after a humiliating defeat.
In Ray Bradbury's short story "Fever Dream", a sick boy suffers a form of this: he's being taken over by rogue cells, which control him bit by bit, for instance his hands, and finally his mind.
The second worst poet in the universe, according to The Guide, was killed by his own major intestine acquiring sentience and throttling his brain to save the universe from his poetry.
Jumpman series: In a very odd variant, Jules' brain seems to be a seperate sentient advisor from his consciousness. Also, the brain makes comments about when it first met a time jump it shut up because it had to argue with itself. This implies every last cell (or atleast every neuron) is at least somewhat sentient.
In Harry Potter the magically created silver hand Voldemort gives to Wormtail seems to be under Wormtail's control, until it strangles Wormtail to death when he hesitates to follow an order.
The titular character of Bill the Galactic Hero has his left arm replaced with the right arm of a bunkmate in the first book. Tembo's arm seems to still retain the memories of its former owner and will make a fist when in the presence of old rivals.
In The Hitchhikers Guide to The Galaxy, the notorious alien poet Grunthos the Flatulent died after a particularly bad recitation when his own small intestine tried to save the audience from further torment by throttling its owner's brain.

Live-Action TV

In an episode of Seinfeld, Jerry's girlfriend forces him to read scripts with her as she horribly overacts, and representations of his brain and penis engage in a chess match to see whether or not he'll dump her.
In Herman's Head, his head is the one controlling things, with bits of his personality disagreeing.
The "breast brains" concept in Coupling. Not to mention Patrick's penis.

Susan: Does you dick do all the thinking for you?
Patrick: I don't know I'll ask him.

In Steven Moffat's sitcom Joking Apart, the lead character's penis gets his own episode - sort-of. He's had a blow to the head and is hallucinating.
In a sort-of-live action example, (Puppets, to be specific), Magellan, the dragon (But not The Dragon ... Well, maybe.) of Eureeka's Castle simply never managed to get control of his tail.
In the Scrubs episode "My Best Laid Plans," J.D.'s penis (informally known as "Mr. Peeps," and speaking in a British accent) tries to get him to sleep with Molly when his girlfriend, Kylie, won't sleep with him. Later, when Kylie is finally ready to sleep with J.D., he admits that he was hanging out with Molly instead of Kylie, which gets him dumped and incurs death threats from Mr. Peeps.
On Angel, lawyer Lindsey had "Evil Hand Issues", after Angel chopped off his hand, and his Evil Lawyer Bosses, Wolfram & Hart, gave him a new one.
This happened three times in Red Dwarf, to Rimmer (a holographic crewmember maintained by the ship's computer):
- At one point gets his body taken over by the ship's computer AI, forcing him to do exercise up until he faints... and even after (his body jogs on, with his head lolled to the side).
- At a different point, the ship AI plays a trick on Rimmer by giving him someone else's arm... and the arm attacks him repeatedly, including poking him in the eyes and grabbing him by the nuts.
- And a third one: when something goes wrong with the hologram suite, Rimmer's lower half begins running around by itself, and Rimmer's upper half complains about it.
One of Murdock's delusions on The A-Team involved his left hand using this trope, although it was more of a nuisance than actually evil. He names it Lefty.

Newspaper Comics

At least two Peanuts strips had various parts of Snoopy's body expressing opinions of their own—usually connected with jogging, which meant the feet said a lot. One of these strips ended when his heart commented, "Just remember, boys -- if I go, we all go!" to which the feet remarked, "That's scary!" and another part said, "Shut up and keep jogging".
Pooch Cafe has occasional strips in which Poncho's various body parts (usually the brain and stomach) argue.
Pearls Before Swine has Pig's suglasses-wearing brain, frustrated with being underused, step out of Pig's head and go on to have a life of its own, successfully winning Jeopardy! and becoming something of a lady's man. It eventually skipped town in favor of an extensive stay at a spa resort for runaway brains.
A series of Zits strips involve Jeremy's brain deciding to go on strike right before a big test.
The Wicked Willy cartoons by Peter Mayle and Gray Jolliffe featured a man with a talking penis. They are widely regarded as the tackiest cartoons ever produced. Quite funny, though.
Vajee: do we need to mention what organ she is? The style of the art is very similar to Wicked Willy, but the cartoons weren't quite as funny as Willy overall. Some were hilarious, though.
A Beetle Bailey strip had a similar concept to the Peanuts one, with all of General Halftrack's body parts complaining as he tried to go to sleep. (Well, almost all - The Comics Curmudgeon was surprised there was no complaint from his poor, overworked liver.)
My Cage features scenes inside Norm's head, where his brain, heart, and libido often have it out with each other.
Garfield's feet have been known to literally fall asleep, while he's still awake. And he's jealous!

Tabletop Games

An occasional frustration for the Frankenstein lineage in Promethean: The Created is that their limbs and organs sometimes run under their own control. This leads to, among other things, one eye sometimes insisting on looking in a different direction. Other lineages have this problem on occasion, but it happens most often to Frankensteins because they're always made of multiple corpses. There is, however, a merit called "Residual Memories", which can grant the Promethean bonus dice on skill rolls - because his body parts retain memories of the skills in question. (When the dice are exhausted, though, the risk of the body parts getting out of control goes up.)
In Mage: The Awakening, there's a particular Abyssal entity called Flesh Intruders, a highly intelligent race of parasites who manifest in tainted organ transplants. Over the period of their gestation, they reform their host's organs to ones suiting their goals, until they literally hatch from the organ, totally suppressing the host's mind in the process, while they still remain aware. The kicker? Every organ that was infected was actually a victim of Sinister Organ Qigong, so not only is there a crazy monster running around, you can bet there's somone whose watching all this and laughing.

Theater

Me and My Dick by Team Starkid is a musical comedy about teenages learning the complexities of relationships by talking to parts of their body like their genitals, (usually, they have names like Dick or Miss Cooter), and other parts, like the heart. The main character's heart thinks Bill Pullman is the greatest actor of our generation.

Video Games

Ocelot was controlled by the transplanted arm of Liquid Snake in the Metal Gear Solid series, possible due to being the son of the Sorrow, a spirit medium. Later, to overcome this he has the arm removed but uses hypnosis and nanomachines to fake it in order to confuse his enemies. Its All There in the Manual. The Metal Gear Solid Database to be precise.
Subverted by Hugh Bliss in the last episode (Bright Side of the Moon) of the first season of Sam and Max by Telltale Games. Max's hand, stomach, and tail are literally removed from his body and then become separate copies of Max, personifying his senseless violence, greed, and sloth. Sam is horrified. Max is (somehow) able to continue to function, although he's definitely not himself.
In Toribash, severed limbs can still be controlled if they have joints still intact. This makes dismembering yourself for some moves a valid strategy.
In World of Warcraft, the Headless Horseman is a boss who appears only during the Halloween event; when reduced to zero hp, his pumpkin-like head (his Soul Jar detaches from his body, yelling "Get over here you idiot!" at his body; eventually it does, and the Boss as a whole regains all his hp. The players can only defeat the Boss by reducing the head to zero hp.

Web omics

Seen with Guere's arm in Miamaska.
Used occasionally in Something*Positive. When PeeJee gets offered a job at a bar, complete with on-the-house drinks (and her liver makes a sound like it's having an orgasm). When she tells Jhim, the gay man on whom she's crushed for years, that she can't think of anything else she'd like their relationship to be, her vagina thinks, "I can!".
In CRFH, Roger's hand occasionally becomes self-aware and autonomous.
In The Noob, Ohforf's crotch agrees to go on a suicidal quest against the brain's will when Hypatia says she might "do anything" for a man brave enough to go.
In Girls with Slingshots, Hazel's ovaries often speak up to tell her that My Biological Clock Is Ticking. And McPedro's mustache has run away from him. In addition, McPedro's mustache is French.
In Digger the Hag is sufficiently skilled at surgery to re-attach severed body parts, but there is a slight chance that they'll go evil and try to kill their owners. As she points out, this is more of a problem with arms than with earlobes, which rather than trying to throttle you just wiggle aggressively. Specific mention was made of a suicidal re-attached toe that tries to stub itself at every opportunity.
One of the character in Sexy Losers is a guy with a talking penis. It's a total Jerkass who makes the guy's life a living hell.
Even though it was not actual verbal communication, Ki from General Protection Fault experiences her own uterus going 'TWINGE' and triggering near uncontrollable lust in these strips of year 2001.
Occurs in Spinnerette with the eponymous character's six arms sometimes acting on their own. Lower-lefty in particular appears to have a thing for her teammate, Mecha Maid.

Web Original

In Mortasheen, this often happens to zombies and creates monsters, with the parts usually being the stomach, the brain, and the placenta, or a recently birthed Zombie Spawn.
An Akatsukis Life takes this to its natural extreme, with an entire crowd of Kisame's taste buds reacting to the word "Spaghetti".

Podcast

The Ricky Gervais Show: Among the many insane beliefs of Karl Pilkington is that his body parts have a will of their own. Typified by his oft-repeated question "So, am I in control of me brain, or is me brain in charge of me?"

Western Animation

Occurred on The Simpsons several times, especially to Homer.
- For example...

Homer: The last bar in Springfield. If I can't get a beer here, I'll have to quit drinking.
Liver: Yay!

Or in the episode where they joined a cult that forbade alcohol...

Marge: Would you like a tall, frosty one, Homer?
Brain: No! Must resist! I love The Leader!
Stomach: Go on! Give in! Beer!
Feet: Ooh, these nylon socks sure are comfortable!

And again:

Brain: Don't say revenge. Don't say revenge.
Homer: Uh... revenge.
Brain: That's it, I'm outta here. (receding footfalls) (door slam)

This is Homer visiting the Cider mill:

Homer: Twenty of the suckiest minutes of my life.
Ned: Ho ho ho, suckin' down the cider, uh? Hey, word to the wise -- [shows Homer a card] season pass! It pays for itself after the sixteenth visit. You know, most people don't know the difference between apple cider and apple juice, but I do. Now here's a little trick to help you remember. If it's clear and yella', you've got juice there, fella! If it's tangy and brown, you're in cider town. Now, there's two exceptions and it gets kinda tricky here...
Homer's Brain: [moans] You can stay, but I'm leaving. (brain floats away; Homer stares blankly for a second, then collapses)

Homer is frequently shown to be stupider than his own brain, and frequently argues with it, to the point where Homer has to ask his brain to explain how money is more useful than a peanut (it's because money can be exchanged for goods and services).
Marge's Beehive tends to nag her. Well, the lower part. The upper part reassures her. The top admits it is nothing but hair and has no opinion on the matter.
On a Treehouse of Horror, Snake is finally put to death, and his hair is donated to Homer. Homer then becomes Snake and takes revenge on all the people responsible for his arrest. Also, Voices Are Mental.
"Shut up, Brain, or I'll stab you with a Q-Tip!"
Even done with Lisa's brain a few times.

Homer: It's just like David and Goliath, except this time David won!
Lisa: (groan)
Lisa's Brain: Yeah, I heard it too. Here's some music. (plays Für Elise)

Better still:

Lisa's Brain: You do realise they're only pretending to like you because of the pool?
Lisa: Shut up, brain! I don't need you any more; I have friends now!

There are several gags in Chowder in which the title character is conversing with his own stomach. Chowder once had a conversation with the representation of his self-esteem, manifested as his own hand.
- In "Taste Buds", Chowder's tongue is strengthened and ends up dominating the rest of his body, dictating what he will eat and beating him up if he does not comply
A character who has conversations with his stomach (actually, it's more of a slave/master type relationship) is Jay Sherman on The Critic.

"Now dance for me!"

Due to an assassination attempt, all that was left of Hector con Carne in Evil Con Carne was a disembodied brain and a disembodied stomach with a mind of its own, originally used in the pilot cartoon for the sake of a cheap pun on the phrase "listen to your gut."
Mucha Lucha: All of The Flea's organs have autonomy, and get out of his body to save him from an evil doctor that wants to extirpate one of them.
A recurring gag on Brandy and Mr. Whiskers involves Whiskers' brain (who has a Yiddish accent, for some reason) literally packing his bags and leaving through Whiskers' ear, usually announcing "You're on your own!". Hell, it became a plot point later on.
Princess Clara's "Octopussoir" from Drawn Together, to the extent that when it's removed from her body, it has an independent and fulfilling life. Also Octopussoir's replacement, Vajoana.
In the Darkwing Duck episode "Aduckyphobia", DW once acquired four extra arms after being bitten by a radioactive spider. They didn't always do what he wanted them to, especially Number Six.
In The Drinky Crow Show almost every character's organs have come to life at some point (usually in overly gruesome detail). Drinky even throws his brain out at one point (much to the relief of his liver) because it keeps telling him to drink.
The Penguins of Madagascar: King Julian gets into a squabble with his own brain while congratulating himself on using his muscle-enhanced naive mouse lemur henchman Mort to intimidate the other zoo animals to giving their stuff to him.
In Spliced, Entree made a bet with his brain, heart and stomach that he could survive a week without them. They left his body for the duration of the bet and spent the week getting into trouble on the island.
Happens to Krypto the Superdog when exposure to red kryptonite caused his tail to gain sentience and separate from his body to cause trouble.
Freakazoid!: The protagonist once had his own sidekick named Handman in "The Sidekick Chronicles," which happened to be his own hand with eyes drawn on it, and a voice provided by his ventriloquism. What's more, Handman then had an affair with Freakazoid's other hand, who both shared a long, kissing sequence (which was graphic even for a kids show) and married among a wedding made up of the cheering, dressed hands of the guests. Despite losing his sidekick, Freakazoid hopes to gain a daughter... or an upper hand. Unlike his hand couple, however, his feet are in a very rocky relationship.
Family Guy: Adam West is so crazy he struck up a relationship with his hand and even tried to marry it. His other hand, however, rejected the proposal. Priest: "If anyone has any reason as to why this marriage should not take place, speak now or forever hold your peace." (Adam West's other hand raises up) Adam West: "Shut up, you had your chance!" (There actually is a joke in there. For something by Seth MacFarlane, it's incredibly subtle. Did you get it?)
South Park:
- "Fat Butt and Pancake Head": For a report on Cultural Diversity, Cartman chooses to do one on Latinos in the arts with the help of a Jennifer Lopez hand puppet. Later, at the mall, the puppet gains autonomy and insists they make a music video, which launches the hand puppet's musical career. Ben Affleck falls in love with the Jennifer Lopez hand puppet (whom he thinks is actually Jeniffer Lopez), and strikes a relationship with it (who both have sex). Then the REAL J-Lo shows up to protest the hand's authenticity. When things get out of control, the hand reveals its real identity by removing "her" hair and, in a male voice, making a confession that she is not 'Jennifer Lopez', but 'Mitch Connor', a con man who has been moving around from town to town. He apologizes to Ben for playing around with his love and states that he will die because he has recently consumed a cyanide pill. After the hand "dies", Cartman is left in control of his hand again. What makes the entire situation funnier is that everyone besides Kyle thought Cartman's Jennifer Lopez hand puppet was really Jennifer Lopez.
- She/he/it returns again in South Park's 200th episode disguised again as Jennifer Lopez, aiding a group of celebrities led by Tom Cruise aiming to suck out the prophet Muhammad's goo so they can empower themselves and not be made fun of. unbeknownst to them however, she planned to take the goo for herself and sell it to the highest bidder.
- In "A Million Little Fibers" Oprah Winfrey's vagina and ass, starved for attention, decided to take hostages and have a shootout with the police (don't ask).
Ugly Americans: As Mark's zombie roommate, Randall's penis once separated from his body in "Treegasm" and attempted to board a bus to Bufallo at Port Authority (apparently traumatized by what Randall put it through). Under a set of guidelines put down by his dick, they both made up and Randall promised to treat his member as an equal.
Fanboy and Chum Chum: Fanboy's weeks of unbathing caused his own stench to animate his hand under the name of Stinks. It had mushrooms for eyes, and had the personality of a mobster.
Courage the Cowardly Dog: Eustace's foot gets infected with a fungus that turns it into a gangster that forces the others to commit crimes for him.
Adventure Time: The Ice King's heart leaves his body to seduce Bubblegum Princess, then cut out her heart and make it his bride.
In El Tigre, Manny uses science/magic to grow a large mustache, which he names Raul and has a mind of its own. It even gets Brainwashed and Crazy!
The opening of the Arthur episode "Arthur's Knee."
Reason And Emotion, a 1940s Disney Wartime Cartoon, demonstrates how the two forces (anthropomorhised into tiny people) fight for control at the 'drivers seat' of the brain.
In The Amazing World of Gumball, Gumball's brain leaves his body when Gumball tries reading a book, and spends the rest of the episode outside it.
In Beetlejuice, the title character's head can detach from his body, and the two are known to argue a lot when that happens.
A Running Gag in Evil Con Carne, Hector's stomach has a separate personality from his brain, and can talk.

Real Life

Older Than Feudalism: Ancient Greek and Roman doctors commonly believed that the uterus could wander around a woman's body, inciting her to madness. This is where we get the concept of "hysteria" from. In the 19th century doctors were still curing hysteria by inducing "hysterical paroxysm" (basically, women's uteruses just make them sort of crazy and it's better to let all that crazy out in one big spasm). How did they induce this full-body spasm? Why, by massaging the clitoris, of course!
The idea that men think with the wrong head. And by the wrong head, we mean the head of the penis.
Bit of Truth in Television: check out the enteric nervous system, complete with neurotransmitters. Takes "thinking with your stomach" to a whole new level, doesn't it?
Each of an octopus's eight arms carries its own individual brain, capable of controlling the arm even after it's been severed. During the animal's daily life, the central brain decides what each tentacle ought to accomplish, but the tentacle gets to decide how to go about it, and the easiest way for the octopus to determine where a tentacle is and exactly what it's doing is to look at it.
Alien hand syndrome is this. Also called "Dr. Strangelove Syndrome" for obvious reasons, mein Führer.
Human (and animal) reflexes occur without any conscious thought. The purpose of most reflex actions is to withdraw a part of the body that is being exposed to harm from the harmful situation as quickly as possible. If you had to think about it consciously, it would add a few vital tenths of a second to the reaction time which could result if a lot more damage being done. For example, the reflex that causes to withdraw your hand from extreme heat is triggered at the spinal cord. It's also why the pain of getting burned doesn't hit until a second or so after the burn occurs. The spinal cord will have already withdrawn your hand before the pain stimulus reaches your brain.