The Vivillon with the Pokeball pattern is currently being distributed in Pokemon X and Y for a very short time in North America. August 12 is the last day to obtain your Vivillon.
UPDATE: The Vivillon is now available to European and Australian players from now until September 8, 2014.
Here are the steps to obtain your Vivillon:
1. Connect your Nintendo 3DS system to the Internet.
2. Select Mystery Gift on the main menu.
3. Select Receive Gift, then Yes.
4. Select Get Via Internet, then Yes.
5. Watch as you receive Poké Ball Pattern Vivillon!
6. Speak to the delivery girl in any Pokémon Center to receive your Vivillon.
7. Remember to save your game!
http://www.pokemon.com/us/pokemon-news/poke-ball-pattern-vivillon-takes-flight/ ... read more