*A reminder to please save your game before trying this glitch in case something goes wrong*
I am calling this glitch the "Pokemon League Dig Glitch".
To activate glitch:
1. Insert Pokemon Black
2. Go to the Pokemon League
3. FLY from the Pokemon League to Victory Road
4. Enter Victory Road
5. From the cave, have a Pokemon use DIG
6. Push and hold UP on the Dpad while the screen is still white
7. Continue to hold UP. You will appear INSIDE the doorway of the Pokemon Center in front of the Pokemon League. You will not be able to move forward, left, or right, and the game will make bumping noises as if you are running into a wall. However, if you move backward, you are able to enter the Pokemon Center.
Try it out!