You can get pokemon like Flaffy in B/W 2 but not in Black and White 1!?(with no nat. dex)
I was told, and I also heard, it's a remake!
Why is that
In Pokemon Black and White 2 the unova pokedex now consists pokemon from other generation including flaaffy, psyduck, riolu and beldum. Check out the black and white 2 pokedex http://pokemondb.net/pokedex/game/black-white-2
Remake doesn't stand for exactly the same.
You may remake something to improve it.
This is going to be like platinum so they have spiced things up with new Pokemon introduced.
Theres going to be many changes including new gym leeders.
They have obviously extended the local dex as well just like platinum.