So, the alternate mirror world has an upside-down Triforce motif. And (Skyward Sword spoilers, for those that care)Is there some significance?Demise's evil Master Sword - i.e. Ghirahim's sword form - also has an upside-down Triforce symbol on it.
Since the Majora's Mask can be seen in the game shop, I bet the connection is to termina (which had the inverted triforce too). But you know, they probalby have linked both things.