Cinderella

Cinderella is one of the classic Disney characters who appears in Kingdom Hearts. The main character from the 1950 film Cinderella (1950 film), she plays a small but important role in the game as one of the Princesses of Heart. Her world was destroyed by Maleficent, but she was taken into captivity.

Kingdom Hearts
She was taken and held deep within Hollow Bastion until all seven Princesses were collected. It is unknown when she was captured but from scenes it can be assumed it was before Snow White and Alice placing her as either 2nd captured or 3rd either before or after Belle.

Once her heart was restored, she stayed behind in the castle of Hollow Bastion to hold back the darkness lurking out of the Final Keyhole, until Sora returned and closed it. Though the Final Keyhole was sealed, Cinderella and the others could feel another dark power approaching from somewhere else (End of the World where Kingdom Hearts was held), and asked Sora to stop Ansem from fulfilling his evil plans.

When Kingdom Hearts was sealed she was returned to her own world.

Kingdom Hearts II
Cinderella is absent in Kingdom Hearts II, though her name was part of the password that allowed access to the DTD dataspace in Tron's world.

Birth By Sleep
She will, however, return in the upcoming PSP game Kingdom Hearts: Birth by Sleep. The latest trailer implies it is Ven and her faithful mouse friend Jaq who created her dress and somehow give it to Fairy Godmother to cast on Cinderella. However, Ven had an obstacle : Lady Tremaine's (Cinderella's wicked stepmother) equally evil cat Lucifer.

Abilities
Because Cinderella is a Princess of Heart, her heart holds part of the ability to open the Final Keyhole that leads to Kingdom Hearts. She also has the power to hold back darkness using the light stored within her heart, a power which she and the other princesses can utilize alone (the exact way she fights off darkness is currently unclear).

In addition, her heart (along with that of the other princesses) can be used to create the Dark Keyblade, which allows the bearer to unlock anyone's heart.

Cinderella (along with the other princesses) can also upgrade other people's powers, as revealed when they upgraded Sora's Fire spell to Firaga.

Trivia

 * It is highly possible that she is the second princess to be captured after Aurora.
 * Birth By Sleep sets ten years before the original Kingdom Hearts, yet Cinderella remains young and beautiful. It is possible that she is immortal because of her status as the Princess of Heart, or she could have been kept young by Maleficent's magic while she was held captive.