Megara or Meg is a character originally from the Disney movie Hercules. In Kingdom Hearts II she is from Olympus Coliseum. Although Olympus Coliseum appeared in Kingdom Hearts, Meg was not present in the first game.
Kingdom Hearts II
Upon Sora's first Kingdom Hearts II visit to the Coliseum, he rescues Megara from a pack of Rabid Dogs. Meg had been on her way through the Underworld looking for Hades, hoping to convince him to give Hercules a break. Sora offers to do this task for her and she happily accepts. She is later kidnapped by Hades as bait for Sora to unlock the Underdrome. After Sora returns to the Olympus Coliseum, he finds it being destroyed by the Hydra. During this boss fight, Megara sits on the side lines and drops HP and MP balls as Sora passes by her.
During Sora's second visit to the Coliseum, he, Hercules and the others are forced to participate in the matches of the Underworld Coliseum. After finding out that Auron is being controlled by Hades, Hercules distracts Hades while Sora and the others go to find the little statue that holds Auron's heart hostage. Upon returning Auron's heart, Hades throws Megara into the stream of River Styx, Hercules then sacrifices himself to save her and restores his confidence in the process.
During the ending credits, she is last seen being with Hercules, Phil and Pegasus beholding the restoration of the Olympus Coliseum.
Origins
In the Disney movie Hercules, Megara is a young woman who gave her soul to Hades in order to save her former lovers life, and thus is required to obey Hades. He sent her to discover Hercules' weak point, but she fell for him instead and turned on Hades. This ultimately cost Meg her life, but Hercules rescued her from the Underworld, reuniting them. Meg's debt to Hades is completely cut out of the Kingdom Hearts II storyline, although Hades does use her as bait in a similar manner.