Xenoblade Chronicles 3D is the first game that can only be played on the New Nintendo 3DS, but of course someone had to try it in a regular 3DS anyway.
Fortunately, the handheld didn't self-destruct or activate a latent sentience program and slowly begin to take over the world (that we know of yet...), and instead displays a simple message that "This is New Nintendo 3DS software and cannot be used on this system."