I also found a "glitch."
The cave where you find Mewtwo within the Safari Zone. A trainer with a Kingler and a Tentacuel. (Can't spell, sorry)
Everything is fine up until his 3rd and final Pokemon: ?????
If you attack it, your game/ROM freezes.
I thought I would let you know. Sorry to bother you if you've already discovered it.
-Jensei.
EDIT: Please disregard this. It seems you've already figured it out.