New Pokémon in X and Y, check the link for pictures, but don't click it if you don't want to see what they look like
A wild hacker appears! It uses Modify Code! It's super effective! Kotaku reports a hacker has discovered three normally unobtainable Pokemon hidden away in the game's code. The new Pokemon are Volcanion, Diancie and Hoopa, which are pictured above, in that order. While not officially confirmed by Nintendo, Game Freak or The Pokemon Company, these Pokemon are thought to be "event Pokemon," which means players who don't hack the game can only catch them at official Pokemon events.
Smealum, the same hacker who created the homebrew Portal game for DS, claimed responsibility for the hack, and also revealed Mega Evolutions for Latios and Latias. While the two Dragon-type Pokemon were previously differentiated by Latios being blue and Latias being red, it seems that they are more or less indistinguishable from each other when they Mega Evolve. The Mega Evolution for Latias is pictured above.
Don't rush off to trade your Pokemon just yet, though. Smealum wrote on Twitter he does not plan to release the hack or any of the newly-discovered Pokemon into the wild. Smealum wrote that while it would be fun "in theory," he didn't want to "ruin" the online Pokemon X / Y experience.
http://www.joystiq.com/2013/11/02/report-hacker-leaks-three-new-pokemon-two-new-mega-evolutions/
NOTE: I haven't been keeping up with my Pokémon X any Y news lately, as I am already moving into other games now, so it's possible this is old news.