Mario
Once you obtain 8 stars, enter the rec room and unlock the 8 star door. Jump into the Mario picture and defeat Goomboss to obtain the key for Mario's Room.

Red ! Boxes
After obtaining 14 stars, stand on the Sun carpet in the main plaza. Enter first person view mood and look up to the beam of light. In the new world, stomp on the red switch in the middle tower to unlock the red ! boxes.

Luigi
After unlocking the red ! boxes, go to the castle courtyard. Punch the giant boo with the cage inside of him to enter Big Boo's Haunt. Obtain the first star by defeating all the Boos to get the staircase. In the second goal, as Mario, go up the stars and into the room with the single bookshelf. Use the fire flower to float up to the room above, where you'll find a Luigi painting. Jump through the painting and defeat Big Boo to get Luigi's key.

Wario
After obtaining 30 stars and defeating Bowser for a 2nd time, head up to the second castle floor and enter the room where Snowman's land. On the left you'll see a Luigi painting, but its reflection in the mirror will be a Wario painting. Get the flower to turn invisible and walk through the mirror to appear on the opposite side. Jump into the Wario painting to enter the level. Defeat Chief Chilly to obtain the key for Wario's Room.

Mini-Games
Here are the locations of the hidden rabbits that unlock mini-games. You must find the rabbit with the specified character.

    * Lucky Stars mini-game: Near entrance to Bob-omb Battlefield with Luigi.
    * Mario Slot mini-game: In the secret room with the Mario painting with Luigi
    * Memory Master mini-game: Near entrance to Wet Dry World with Luigi.
    * Mushroom Roulette mini-game: In area near the columns that drain the moat with Luigi.
    * Pair-a-Gone mini-game: In the hedge maze with Luigi.
    * Picture Poker mini-game: In the courtyard over the entrance with Luigi.
    * Super Mario Slot mini-game: On top of the Castle with Luigi. Must have 150 stars.
    * Bounce and trounce mini-game: Near the entrance to Lethal Lava Land with Mario.
    * Connect the characters mini-game: Near the entrance to Lethal Lava Land with Mario.
    * Shell Smash mini-game: In the moat after it is drained with Mario
    * Shuffle Shell mini-game: Near the entrance to Snowman's Land with Mario.
    * Sort or 'Splode mini-game: Near the ledge over the waterfall with Mario.
    * Trampoline Terror mini-game: Near the entrance to Wet Dry World with Mario.
    * Trampoline Time mini-game: Near the entrance to Jolly Roger Bay with Mario.
    * Giant Snowball Slalom mini-game: In the alcove across from Rainbow Ride with Wario.
    * Bingo Ball mini-game: On the right side of the castle when facing it with Wario. (Near the trees)
    * Coincentration mini-game: Near the entrance to Whomp's Fortress with Wario.
    * Intense Coincentration mini-game: Near the entrance to Tick-Tock Clock with Wario.
    * Lakitu Launch mini-game: Near the entrance to Tiny-Huge Island with Wario.
    * Psyche Out mini-game: In a corridor near Lethal Lava Land with Wario.
    * Slots Shot mini-game: In the courtyard behind the fountain with Wario.
    * Boom Box mini-game: Near the main bridge with Yoshi
    * Hide and Boo Seek mini-game: Outside near the main bridge with Yoshi.
    * Mix-a-Mug mini-game: Near entrance to Lethal Lava Land with Yoshi.
    * Puzzle panel mini-game: Outside of the main bridge with Yoshi.
    * Puzzle Panic mini-game: In the moat after it is drained with Yoshi.
    * Tox Box Shuffle mini-game: Outside in a flower patch near the wooden bridge with Yoshi.
    * Which Wiggler mini-game: Outside in the hedge maze with Yoshi