On the title screen, when "Search for Mario" and "Continue Search" text is displayed, press L + R + Start + Select on controller 2. This opens a hidden menu where you can select the Castle ...
Go to world 1-3 and find a potion. Now find the vase next to the brick building all the way to the right side of the level. Drop the potion and go into Sub-Space and then warp into the vase (stand ...