What happens when you scan your 31st Amiibo in Amiibo Tap?
The first 30 Amiibos you scan unlocks a random locked game, tied to the Amiibo, but not necessary related to its character (Mario may unlock The Legend of Zelda, for example).
Each Amiibo scanned after the 30th will unlock a random (already) unlocked game, which will also be tied to the Amiibo.
This will not break the liaison between the Amiibo that previously unlocked and the twice unlocked game, meaning that tapping any two Amiibos will let you play the game, and switch between scenes like if both Amiibos were the same one.