Heart

A heart is a recurring element in Disney media. There are two games that use this concept.

Kingdom Hearts series
"The heart may be weak, and sometimes it may even give in... But I learned that deep down there's a light that never goes out."

- Sora to Ansem, Seeker of Darkness

Construction
What actually makes up a heart is a mystery in the Kingdom Hearts universe. Much research has been done to try and unravel the mystery, most notably by Ansem the Wise and his apprentices. However, this research only served to lower the barriers between worlds, set up the events for Kingdom Hearts, Kingdom Hearts: Chain of Memories, and Kingdom Hearts II, and cause many worlds to be plunged into darkness. It is known, however, that the heart is primarily made up of light and darkness, the latter of which formed due to people's greed. The exception to this are the Princesses of Heart, maidens whose hearts are free of darkness.

The heart appears to be responsible for the composure of memories, will, goals, and ambitions, as is the case in the transfer of Master Xehanort's heart into Terra and the internal struggle of wills inside Terra-Xehanort.

The heart is also responsible for emotions, as beings lacking one, such as the Nobodies, cannot feel emotions.

Tie-in to the Worlds
According to legend, the worlds were one and united through the light in people's hearts. Once these hearts became filled with darkness, however, chaos resulted, and the worlds were separated. It was the light that remained only in the hearts of children that would keep the worlds in existence before they were shrouded in darkness completely.

Ansem's Research
Scholar Ansem the Wise was struck by a great curiosity of the heart and its true nature. He began research on the topic so he could better protect his world from the forces of darkness, together with his six apprentices, and started to write his reports. However when Ansem reliazed that his experiments could bring disaster to the world he stopped all his research.

However Xehanort decided to continue the experiments and realized that when hearts were seduced by darkness, a creature he dubbed a "Pureblood Heartless" was born. He made note of how Heartless acted on instinct, and wished to try creating his own Heartless. To tell them apart from the Purebloods, he dubbed them "Emblems" and christened them with what would later become the Heartless insignia. He made note of how they behaved relatively the same way, continuing to experiment in other areas with which the heart was concerned. He had no idea that he had caused chaos to brew. However when Ansem became aware of Xehanort's activities, he ordered that his research be stopped at once. This strict request would lead to the birth of Ansem and Xemnas, as well as the rebellion of Ansem's other apprentices. Xehanort and the other apprentices' Nobodies would later grow to form Organization XIII, a group that had the sole purpose of unlocking the secrets of the heart.

While Ansem was cast out into the Realm of Nothingness, Xehanort wrote the Ansem Reports. After he put his research and his findings to paper, these reports scattered across the worlds, and were able to help the residents of Traverse Town and Sora in his first journey when it came to learning about and fighting the Heartless. Ansem's experiments on the heart would continue to haunt him even after his escape from the Realm of Nothingness, throughout the story of Kingdom Hearts II, as his reports continued to spawn as the Heartless he had created returned. He was forced to recall his past mistakes and even failed to succeed in avenging his dignity, realizing all his experimentations had gotten him nowhere. Upon his supposed death, which instead erased the majority of his memory and sent him to the Dark Meridian, one of the last things he would hear would be Xemnas's accusations that he was the source of all Heartless, and that the chaos and turmoil that had resulted over the past years were all his fault.

The Seven of Pure Light
Supposedly, seven maidens existed with hearts of pure light, whose hearts when joined as one could unlock Kingdom Hearts. It was for this reason that the maidens, called Princesses of Heart, were sought by beings of the darkness who wished to rule the Heart of all Worlds, particularly Maleficent and Xehanort's Heartless. Kingdom Hearts could only be accessed by the completion of a Keyhole in Hollow Bastion, which required all seven pure hearts to be joined as one in the Keyblade of Peoples' Hearts. These hearts were released, however, due to Sora keeping Kingdom Hearts out of the villains' reach.

Powers and Abilities
A cherished element throughout the Kingdom Hearts series, hearts possess many unique powers and abilities. It is for this reason that antagonists seek them. Hearts are able to produce emotion, something that members of Organization XIII crave. As revealed in Kingdom Hearts Birth by Sleep, hearts are also able to sense the emotions of others from outside worlds if they are strong, as seen when Sora feels Ventus's great sadness after the loss of his heart. As shown with Kairi and Ventus, if one's body remains intact when the heart is lost, the person will enter a state similar to catatonia until the heart is restored. Hearts are also able to merge with others or be split, as seen when both Master Xehanort and Master Eraqus join hearts with Terra, and when Ventus's heart merges with Sora's. A much later instance of this would be Kairi's heart merging with Sora's during his first journey. They can be split to produce an embodiment of either the light or the darkness, as seen when Master Xehanort produces Vanitas by unlocking the darkness of Ventus's heart. Hearts can also be merged to create unique Keyblades, major examples being the X-blade and the Keyblade of People's Hearts. These Keyblades ultimately grant access to the grandest of hearts: Kingdom Hearts.

The heart also has a heavy influence on all that lives, having the power to produce Heartless and potentially Nobodies at its loss or corruption by darkness. As the heart grants emotion, negative emotions formed when Vanitas and Ventus were split caused the Unversed to spawn, hence their connection to the heart.

Kingdom Hearts
Kingdom Hearts is the largest and grandest heart of all. The heart of all worlds, it is a source of fantastic power and wisdom, and as such is sought out by many villains for different reasons. The artificial Kingdom Hearts of Kingdom Hearts II takes on the shape of a heart shaped moon, which further reinforces the fact it is the heart of all worlds. Upon a heart's release after the defeat of an Emblem Heartless, these hearts travel to Kingdom Hearts, empowering it, and in the case of the Kingdom Hearts II storyline, benefiting the Nobodies. However, when you defeat a Pureblood Heartless no heart appears.

Heartless
When a being, be they good or evil, gives in to the darkness in their heart, their heart is consumed by it and becomes a Heartless. This new entity separates from the body and soul, which fade into darkness, and begins to act on a primal instinct to gather other hearts and corrupt them. This instinct results in Heartless attacking other beings to increase their numbers, and attacking the heart of a world by means of the Keyhole, causing it to be completely overwhelmed by darkness. Of course, as dictated by their instinct, the Heartless seek out the biggest heart of all: Kingdom Hearts.

Emblem Heartless defeated by the Keyblade give up the stolen heart, which causes it to return to the owner's original body. However, in Kingdom Hearts II, the hearts went to Organization XIII, which may mean there is a way to change the flow of hearts. Hearts will also not return to their owner if a Nobody was formed.The amount of darkness in the heart, as well as the strength of the heart, seems to dictate the strength of the Heartless formed (as the Princesses of Heart contained no darkness in their hearts, they could not create Heartless. Likewise, Sora's heart contained so little darkness, his became a small Shadow, though his heart was immensely strong. This let him keep his emotions and memories instead of fading to the darkness.) The Heartless are arranged in a hierarchical society, with the most powerful Heartless directing the others' actions. This theory was proven by Xehanort whose Heartless went on to control all others.

Nobodies
When a particularly strong heart is turned into a Heartless, the body it leaves behind begins to act of its own accord due to the strong will it possesses, becoming a Nobody. The body of a Nobody may be warped to a degree from its original form, depending on the strength of its heart. Members of Organization XIII all possessed remarkably strong hearts, allowing their Nobodies to retain their human appearance with only minor changes. Due to a lack of a heart, a Nobody cannot truly feel emotions; many members of Organization XIII often pretend that they can, following their memories of their human selves.

Although Nobodies are born as empty shells, they are capable of developing hearts of their own over time. Additionally, the shells can be implanted with the heart of another, becoming a vessel for that heart.

Heart Collection
In Kingdom Hearts 358/2 Days, Organization XIII's heart collection process was greatly elaborated. While on several missions to various worlds, Nobodies of the Organization would seek out as many Emblem Heartless as possible, obtaining a captive heart from those they defeated. The captive hearts would then be absorbed by Kingdom Hearts, more specifically, Xemnas's synthetic incarnation of the world, immediately afterwards. Organization XIII completely ignored Pureblood Heartless, as they lacked the hearts they sought. The heart collection field was strictly where Xemnas found a use for Roxas, Sora's Nobody being the only one amongst their ranks able to actually release hearts, as he wielded the Keyblade (any other Organization member simply caused a Heartless to fade back into darkness when it was defeated, without the released heart side-effect). Xion also possessed this power, as she was Sora, and to a lesser extent, Roxas's replica. While Xemnas planned on having Xion absorb Roxas so he could have the full power of Sora's Keyblade in the end, he desperately wished to reclaim Roxas after Xion was defeated when Sora's Nobody fled the Organization. He did not count on Roxas being captured by Riku in the Nobody's attempt to free Kingdom Hearts so he could revitalize Xion. This forced Xemnas to use Sora himself as an alternative.

In Kingdom Hearts II, Organization XIII switched tactics and used Sora for heart collection, because no surviving member was able to collect hearts after Roxas was absorbed by Sora. Sora remained unaware of his role in Xemnas's plan, sending captive hearts to Kingdom Hearts as he saved each world from the Heartless threat. When Saïx revealed this role to the Keyblade wielder, however, Sora became wary of defeating Heartless, as he did not wish to aid his enemies, the Organization. He had no choice, however, eventually reaching The World That Never Was, Organization XIII's stronghold. When King Mickey met up with Ansem the Wise, the elderly scholar attempted to encode Kingdom Hearts as data with a special device, the Kingdom Hearts Encoder. He realized, upon the machine's self-destruction, that hearts couldn't be encoded as data, destroying Xemnas's synthetic Kingdom Hearts and releasing every heart it held inside before not only his death, but the final battle in Kingdom Hearts itself between Sora, Riku and the Organization's Superior.

It is unknown what became of hearts released in Kingdom Hearts. While Organization XIII did exist, they did not collect hearts until Roxas's birth, after the events of Hollow Bastion, and after he trained with the Organization members featured in Kingdom Hearts: Chain of Memories. It is most logical that these hearts went back to their bodies and returned to their original form.

Although the Emblem Heartless in Castle Oblivion release hearts, they are merely creations of Sora and Riku's memories. Nearly all of the Heartless that appear within are even copies of Heartless the two had seen in their earlier journey.

Unversed
Unlike other enemies seen throughout the Kingdom Hearts series, the Unversed lack a direct connection to the heart. Instead, they are the embodiment of negative emotions, produced when Ventus's heart was split in half by Master Xehanort to create Vanitas.

Keyblade
Currently, the only known requirements to wield a Keyblade are having a memory of wielding a Keyblade and possessing a strong heart, whether it be a heart of darkness or light. This connection is expected to be further expanded on in the series. A type of Keyblade made from hearts also exists. The only known Keyblades of this type are the χ-blade, which is made from a heart of pure darkness and a heart of pure light, and the Keyblade of People's Hearts, which is made from the hearts of the seven Princesses of Heart.

Body
The body (肉体 nikutai) is a recurring factor and philosophy in the Kingdom Hearts series; along with the heart and soul, it is a part vital to the complete existence of any living thing. The body gives the heart and soul a vessel, granting a person a physical appearance and a form. The body is a medium for a person's heart and feelings to be expressed in the physical world.

The Heart controls the body, much like the brain in the real world, so when someone becomes a Heartless, and their heart is released, they leave behind their body and soul, which is an empty shell and usually withers away. However, if that person's heart was strong enough, the soul will take control of the body and the shell will start to act on its own. A body being controlled by a soul with no heart is a Nobody. While the Heart is the deciding factor as to if a person can wield the Keyblade, the body can be used in a loophole for acquiring the Keyblade, as seen with Ansem, Seeker of Darkness and Riku in Kingdom Hearts. Ansem possessed Riku's body, thereby controlling the heart and giving him access to Riku's Keyblade-wielding powers.

Soul
The soul (魂 tamashii), along with the body and heart, is a part vital to the complete existence of any living thing. The soul literally gives the body life, and is the difference between being alive or dead. It is the force that wills the body to live, and drives it to survive.

When someone becomes a Heartless, their heart, which controls the body, is released and the body and soul is left behind. Usually, the body and soul, having no guidance, wither away. However, if that person's will was strong enough, the soul will take command of the body and will it on as a Nobody. Exceptionally strong Nobodies, such as the members of Organization XIII, retain their human form. Therefore, it is clear that will is related and is an essential part of the soul.

Unlike the heart, which controls the body, telling it what to do and giving it feelings and emotion, the soul is the energy and life the body uses to carry out the heart's commands. Essentially, the soul is life. Therefore, it is assumed that the soul is the spirit or ghost that leaves the body upon death. If the soul leaves the body, it has no energy or drive to carry out the heart's orders, which ultimately causes the being to die.

When the will is exceptionally strong, the soul can live without both the heart and body, as was the case of Terra's Lingering Will; a suit of Keyblade Armor made animate by Terra's disembodied soul.

Epic Mickey series
A Heart is a major plot point in Epic Mickey. Any cartoon character who is loved by many has a heart of their own. All cartoon characters who have a heart reside in the Toon World. Otherwise, once forgotten or retired, they are sent to The Wasteland and their heart disappears. The game's novelization states that people who lack Hearts feel hollow, abandoned and empty. Mickey Mouse has the most powerful heart of all, and the villains of Wasteland (by far mostly the Shadow Blot) want to use it to escape their imprisonment.

In the first game, The Mad Doctor attempts to extract Mickey's heart at the beginning of the game to help the fake Shadow Blot escape Wasteland, but fails.

Near the end of the game, after Mickey has redeemed or defeated the fake Shadow Blot, the real Shadow Blot is accidentally unleashed from the Jug on Mickeyjunk Mountain, who then holds Gremlin Gus and Oswald hostage, and will release them if Mickey gives up his own heart. The deed is done, unfortunately, and now the trio must defeat the Shadow Blot from the inside.

Once Mickey destroys all the Bloticles inside the Blot, his heart is released, only for Oswald to grab it. After realizing that Mickey deserves it more than him, Oswald allows it to go back inside of Mickey's body, before unleashing a barrage of fireworks to destroy the Blot once and for all.

In Epic Mickey 2: The Power of Two, the Mad Doctor plans to become famous again by creating an artificial heart through the toons. Utilizing a television transmitter similar to the one Gus constructs in the opening of the game, the Mad Doctor broadcasts his own television show to the Cartoon World, "The Wonderful World of Evil", and is hoping the ratings there will give him a heart again. To become a Toon once more, he pumps the Guardians from the ground beneath Wasteland in an effort to try and harness their power and get revenge on Wasteland by leaving it in an inert state (his machines were the cause of the surge in quake activity). And with the Brush, he would move to the top of the Disney Villain hierarchy.

Yu-Gi-Oh!
In Yu-Gi-Oh! a Heart is a source of the spirits. In the Virtual World arc, the hearts are a keys to the soul room and bodies are a locks: If the statue is destroyed and not repaired, the victim will die due to severing of body parts, his/her heart was released. Tristan's heart was released after Danny broke him while he was turned into a statue. Doing the same on everyone, Chris sacrifices Yugi's friends with Blue-Eyes Shining Dragon to release their hearts. Jeremie recreates everyone with his People Recreation Program and Chris allows the hearts to go back inside of his friends' bodies, regaining their conscious.

All seven hearts together have same colors as the Rainbow Crystals from Sailor Moon.
 * Red Heart: Duke Devlin
 * Orange Heart: Tristan Taylor
 * Yellow Heart: Serenity Wheeler
 * Green Heart: Joey Wheeler
 * Blue Heart: Téa Gardner
 * Indigo Heart: Danny
 * Purple Heart: Frances

FernGully: The Last Rainforest
A Heart is a major plot point in FernGully: The Last Rainforest. According to Luna, Sailor Moon has the most powerful heart of all and Hexxus wants to use it to destroy all of FernGully.

During the events, Eggman's plan to extract Sailor Moon's heart to help Hexxus destroy FernGully. When Sailor Moon had to stop Hexxus using the power of the Silver Crystal, Decoe and Bocoe steal her Moon Stick, and will return the Silver Crystal if Sailor Moon gives up her own heart to Hexxus. The deed is done, unfortunately, and now Super Sonic must defeat Hexxus. Once Super Sonic releases Sailor Moon's heart, it had been engulfed by Nibiru's energy that had weaken her. He restores the heart with his super powers, healing Sailor Moon from her chest pain, he allows it to go back inside of Sailor Moon's body.

Titan A.E.
A Heart of the Drej Queen, the leader of the Drej, described by Admiral Winfield as "The source of all Drej will" and the main antagonist of Titan A.E.