...till you complete the game. To keep things fresh Nintendo are banning existing Pokemon from the main part of Pokemon Black and White.
According to a blog post from developer GameFreak's Junichi Masuda (translated via Andriasang), the team want to offer a complete reboot for the series - removing previous Pokemon from the adventure.
Your old favourites are only encountered after completing the main game. He wants players both old and new to be in the same boat, trying to recapture the unknown and the feeling of "what does this Pokémon do?"
The studio questioned testers from outside Nintendo, with a results pointing toward a refreshing, new experience:
The latest TV spot (courtesy to Squidboy):