Sora and his friends arrive in Wonderland early in the game and meet the first princess of Heart, Alice. She was accused of attacking the Queen of Hearts and trying steal her heart, and Sora has to prove her innocence by finding the real culprit.
Wonderland is a world in which justice doesn't exist. The Queen, even when Alice's innocence is proved, would still send her guards after Sora, thus giving an opportunity for the Heartless to kidnap Alice.
Alice: Madness Returns
In the American McGee's Alice series, Alice Liddel uses Wonderland as a world in her head to escape from her terrible reality. In Alice: Madness Returns, Alice's Wonderland is being systematically by a gigantic train that looks like a cathedral. Alice's primary goal in the game is to find out what the train is, why the train is destroying Wonderland and how she can stop it.