Just register it before September 30, 2014
The Pokemon X & Y Bank App is coming later this month, and it'll allow you to store your creatures into cloud storage, as well as transfer all your captures from Black or White. We knew all this already, but Iwata has just announced a new promotion during this morning's Nintendo Direct.
If you register your app before September 30th, 2014, you'll get a free Celebi. Neat! You have plenty of time to do this, so you may as well grab the free trial.