In the Japanese version of Tomodachi Life, the Age-o-matic item worked differently, as it only temporarily turned a child Mii into an adult Mii. It is only permanent when used on child couples or mixed adult and child couples who want to marry, and the effect gets immediately cancelled when they divorce.

In the International versions of the game, this was changed so that the effect becomes permanent when used. Because of this, the Kid-o-matic item was created exclusively for the international versions as a way to reverse the effects of the Age-o-matic. (and allowing adult Miis to become children)