Nintendo has begun teasing a special creature for Pokemon X and Y, and in the process confirmed part of a rumor from a hacker who discovered it early. The Pokemon is the legendary rock and fairy type Diancie, and Nintendo says details on how to obtain one will be shared at a later time.
A hacker stumbled upon Diancie in November, along with two others: Volcanion and Hoopa. Since this teaser confirms that Diancie is legitimate, the other two likely are as well. We speculated at the time that these were likely to be given out via special distribution events, and Nintendo's language about being unable to find it during normal play would seem to indicate that.