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Super Mario Advance 4: Super Mario Bros. 3 features e-Reader compatibility, in that it can link up to a second Game Boy Advance with an e-Reader. Upon scanning in one of three types of cards, something will then be triggered in the game. One type of card present in the game are the Switch Cards. These cards had a significant effect on gameplay, in that they generally made massive changes to the game when used. Out of the seven released Switch Cards, only two of them were released outside of Japan. Additionally, unlike the e-reader levels, these features were left out of the games re-release in the Wii U Virtual Console. In total, there are fifteen switch effects, seven of which are unused. Said effects also have unused pop-up icons that were supposed to appear on the Game Boy Advance screen when said effect was activated.
Switches released worldwide
Switches released in Japan
Completely unused effects