Project Red the Fifth Glitch: Walk Through Walls
0*Commentary*
This glitch involves some timing, a ledge and the safari zone. Here's how we do it: first go to the Safari zone. Go in and try to leave, say no to the counter boy's request. Then save, restart and walk out. The game will think you are not in the Safari zone but you are at the same time. So you can walk around outside but you only have 500 steps. Get one of your Pokemon poisoned and walk around. Make sure they won't faint prematurely. Then around the time of the 500th step step over a ledge on the 500th step. The Safari zone should call you back mid air. When you return you'll be able to walk through walls. Now walk until your Pokemon has fainted and return to the front of the last Pokemon center. You can now walk through walls.
For a better explanation on this glitch check out:
http://lparchive.org/Pokemon-Blue/