As you can see above and after the break, the tattoo actually works. Whenever the 3DS camera is looking at his arm, the Mii of his choosing appears to be standing just below his wrist. Cranberryzero says the tattoo works best in dim light; in bright light, the device seems to have trouble sussing out the card's border from his skin color.
It's pretty cool -- and clever -- but he'd better start preparing an explanation to give his future grandkids now.
