In World 2-5, have small Mario climb the vine to the bonus room. Exit the bonus room without powering up, then jump over to the four Question Blocks on your right. Hit the last Question Block to release a Mushroom, then drop down off of the orange blocks, letting the Mushroom follow you into the goal area. Next, jump into the Roulette Block (watch out for the Chain Chomp), and Mario will walk to the right and off the screen like normal. When the Mushroom slides off-screen, a headless Super Mario will appear on the left side of the screen while the power-up sound effect plays. After a few seconds, Mario will perform his small-to-Super power-up animation and start walking to the right again as the game takes you back to the map screen.