Days 23 - 51 take place during the storyline of Kingdom Hearts: Chain Of Memories (2004).
The game was dedicated to the memory of Wayne Allwine, who voiced Mickey Mouse for thirty-two years. This was Wayne's final project as Mickey.
There was suppose to be a Pinocchio (1940) world added to the game, but due to time restrictions, it was recycled and put into Kingdom Hearts 3D: Dream Drop Distance (2012). Some of the sprites of the characters are still in the game's code with Pinocchio as a human, Gepetto, Honest John, and Gideon. Tetsuya Nomura explained that the planned plot for the world was, "Set in a circus and playing off the story of Pinocchio, a puppet with a heart, and the Nobodies who possess no heart." He planned for a sad episode with Roxas and Xion looking for hope for themselves.
With their appearances in this game; Jasmine, Belle, and Kairi become the only three Princesses Of Heart to appear in every game of the franchise as of now.
Sora, Donald, Goofy, Riku, Kairi, and King Mickey are the only six characters to appear in every game of the franchise.