Blue Green Switch

The Blue Green Switch is an e-Reader card for use with Super Mario Advance 4: Super Mario Bros. 3. It was included in the Series 2 set of cards. Although technically a Power-Up card, it was labelled as a "Game Level" card.

Once scanned, grass with turnips below appear all throughout the main game, which Mario can pluck from the ground and throw at various enemies, just like in Super Mario Bros. 2.

English
Make vegetables sprout up in the level, then use them to attack enemies. This card can be used only in the existing game levels. [!]Scan the card once to turn the switch on, and scan it a second time to turn the switch off!

Japanese
オリジナルコースに野菜出現!

Translation
Vegetables appear in the original course!