Yes they are, once you finish the main story and get the national Dex, you can find lower generation Pokemon
a penguin rolling down the hill AndA penguin in a tuxedo
A zebra in an evelvator with a cold
Pokemon Black and White is about to become the champion. During your journey, you encounter new Pokemon, new characters, and new gym leaders. After you become the champion, you set your goal to...
There is no in game Celebi, you need to transfer one from another game.