It's not actually that this game doesn't work at all, it works fine, but the in-game text in the Yoshi's Cookie portion of the game is all garbled. Rather than Japanese characters, the characters are replaced with random symbols, as though a font were missing or something.
I have heard on another forum (though I cannot verify this) that the Japanese version of F-Zero GX has the same problem and that it also occurs when you use a freeloader.
I'm using the latest version of Gecko OS, but it happens on every version I've tried.
I can provide a screenshot if one is needed.