Sugu ni mantan! Power Meter!!

The Cyan Switch is a Japan-exclusive e-Reader card for use with Super Mario Advance 4: Super Mario Bros. 3. It was released in Series 2 in Japan. It can be used in both the main game and in World-e.

Once the Cyan Switch is scanned, the Power Meter is halved, making it much easier to run and fly throughout stages.

Japanese
すぐにまんたん! パワーメーター!!

Translation
Fill it up right away! Power Meter!!