Bank transfer flood gates were momentarily up in Japan
Everyone is still waiting for the full release of the Pokemon X & Y Bank and Transfer App. When that day comes, the proverbial "flood gates" will be opened up, and allow for players to enjoy every single Pokemon from prior generations (all 718).
Well those gates were momentarily opened up in Japan, and some people have already grabbed a bit of footage from these hasty transfers. Serebii has one video in particular that shows off pretty much every legendary you could ask for, including Entei, Lugia, Latios, and more.
I still think it's incredible that Game Freak has provided 3D models for every single Pokemon, and included signature moves on top of that. That's an insane attention to detail.