Jasmine is a case of Truer to the Text, as she's an Action Girl who becomes a Guest-Star Party Member after learning of Jafar's ploy and stays with the party until Genie Jafar is defeated. She still is kidnapped, but here, she falls victim to Maleficent and The Worf Effect.
Kairi, natch. In the games, she is a Damsel in Distress in every numbered game, and she Can't Catch Up with Sora and Riku. Here, however, she starts wielding a Keyblade at the same time as Sora. Her battle with Darth Vader even implied she became stronger than Sora.
Patchwork Fic: Some worlds are this between the source material and the Disney Movie. An example is Wonderland, as the Duchess, who does not appear in the Disney movie, appears here.
Wham Episode: The entire travel between Neverland and Hollow Bastion is this. First off, the Master is revealed to be Dr. Koopa, although that's a Captain Obvious Reveal, since everyone knew that Dr. Koopa is Metallix's master. However, more unsettling is how he banished Kairi to the Null Space so her heart could find her hero (which turns out to be Sora). Dr. Koopa then reveals that the "Kairi" that helped throughout the journey was an illusion created from Kairi's heart, which is inside Sora, Sora's feelings for Kairi, and Dr. Koopa's personal Fix Fic, in the form of making Kairi an Action Girl. It's then revealed that Dr. Koopa's Keyblade (which actually is the legendary X-Blade) is the only thing that can wake the real Kairi, but she'll claim the illusionary Kairi's memories as her own. (Except the X-Blade isn't the only Keyblade which could do it; Dr. Koopa lied so the villains couldn't use the Keyblade of Heart to take Kairi's heart themselves.) Sora, wanting to save Kairi, uses the X-Blade on himself, returning Kairi's heart, but also leading to the creation of his Heartless, his Nobody Roxas, and Kairi's Nobody Namine. Granted, Sora's Heartless ends up on the Gummi Ship, Kairi recognizes it, and uses her light to restore Sora.
Inverted and downplayed. Kairi establishes herself as a badass by singlehandedly defeating Darth Vader. Even then, Vader put one hell of a fight.
Vader himself plays it straight: he curb-stomps everyone in the party, including Sonic, Metallix and Dr. Koopa.
Maleficent establishes herself as the main threat when she kidnaps Jasmine after Genie Jafar's defeat. Except she's not the main threat; the true main threat is Ansem, Seeker of Darkness.
Captain Obvious Reveal, since everyone knew that Dr. Koopa is Metallix's master. However, more unsettling is how he banished Kairi to the Null Space so her heart could find her hero (which turns out to be Sora). Dr. Koopa then reveals that the "Kairi" that helped throughout the journey was an illusion created from Kairi's heart, which is inside Sora, Sora's feelings for Kairi, and Dr. Koopa's personal Fix Fic, in the form of making Kairi an Action Girl. It's then revealed that Dr. Koopa's Keyblade (which actually is the legendary X-Blade) is the only thing that can wake the real Kairi, but she'll claim the illusionary Kairi's memories as her own. (Except the X-Blade isn't the only Keyblade which could do it; Dr. Koopa lied so the villains couldn't use the Keyblade of Heart to take Kairi's heart themselves.) Sora, wanting to save Kairi, uses the X-Blade on himself, returning Kairi's heart, but also leading to the creation of his Heartless, his Nobody Roxas, and Kairi's Nobody Namine. Granted, Sora's Heartless ends up on the Gummi Ship, Kairi recognizes it, and uses her light to restore Sora.