Pokémon Black & White introduce what is called the “High Link” feature. Using this, you can connect locally to a friend’s Nintendo DS and wander about the Isshu region alongside them, taking on a variety of missions along the way.
The depiction of Isshu you see will differ, depending on whether you’re the host or the player joining someone else’s game. If you fall into the latter category, you’ll see a monochrome version of Isshu, and your character will represented by your online multiplayer avatar.
Black & White also features four seasons — Spring, Summer, Fall and Winter — each of which last for a single calender month. One of the new monsters, a Normal / Grass type named Shikijika, changes colour with each season.
Additionally, director, Junichi Masuda, revealed on his blog that Black & White will only feature new Pokémon until an unspecified point later in the game. Game Freak feel that this will allow everyone to start out on equal footing and help recreate the sense of discovery from the first generation games.