Instructions
Turn on the PS3 system and insert the "LittleBigPlanet" game disc into the system's disc drive.
Scroll over to the "Game" section of the XrossMediaBar and select the "LittleBigPlanet" disc icon to launch the game.
Press the "PS Home" button followed by the "X" button on the second controller that you want to use while in the "LittleBigPlanet" pod. This will cause the second player's character to appear in the game.
Repeat Step 3 for the third and fourth controllers if necessary.
Select the game mode that you want to play in. You will now begin the game mode with your friends.