Complete the game with only 50 Stars
Get to the room where you can only enter with 50 Stars. While facing the door, go to the left staircase and jump to the second step. Line yourself up with the corner of this step and the next one so that you are at about a 45 degree angle. Charge up a dash. When you are at about a second away from the corner, slide kick (Crouch + Punch) and hold Up/Left. You should launch up into darkness then fall down. Try to angle yourself so you will land in the room with the portal. Everything should be black and you will hear the endless staircase music. Try to find the hole and jump in. Note: You can do this with any character, but if done with Luigi, Yoshi, or Wario you will die once the Rainbow Road credits end. Sometimes you will die automatically if something went wrong when at the staircase.