Teki Power Up! Tokuten x2!!

The Red Switch is a Japan-exclusive Series 2 e-Reader card that is used with Super Mario Advance 4: Super Mario Bros. 3. It can be used in both the main game and in World-e. Its key artwork is dark green with a red outline of Bowser.

Once this card is scanned on the e-Reader, it makes all non-lethal damage power down the player to Small form (as in Super Mario Bros. and its derivatives, the Japanese version of Super Mario Bros. 3, and the original version of Super Mario World), replaces most of the enemies with more difficult ones (similar to the Hard Mode of Super Mario Bros.), and doubles the bosses' health. However, the points that the player receives are doubled, making the player's score accumulate much faster.

Japanese
敵パワーアップ! 得点x2!!

Translation
Enemy Power Up! Score X2!!