Select a level at the World Map screen, to get to the "Start? Yes / No" prompt. Then, hold L + R to display the password entry prompt and enter one of the following codes to activate the corresponding cheat function.
Enter STARSLOCOROCO as a code.
All the Muimui
Enter ALLCOLORSLOCOROCO as a code.
Enter SLACRLOCOROCO as a code.
While playing, split all of the Rocos apart in a safe place (or at a place where they will not fall). After awhile they will start to play with each other, "dogpile" the person singing the chorus, or line up in a line and count to the numberof Rocos you have in Japanese.
Strategy guides from GameFAQs