I was messing around with my Red game, and discovered a strange "variant" to the infamous Mew glitch. See a video here:
Basically, you do the same thing as you'd always do, but the thing here that causes that dialog box to pop up is you have to heal at the Pok?mon center before activating the glitch. In my case, I had to Teleport to avoid walking onto that route. And yes it's a Gengar… that's just because of who I fought. It should work with any Pok?mon.
Does anyone know why exactly instead of the Start menu popping up, I get a dialog box from the Team Rocket leader? I have a theory, but it's probably wrong… so I'm interested in what you all have to say. I also noticed the random trainer sprite that seems to move as soon as the battle starts (does that even if you do the glitch the normal way), and again, I ask: Why?
PS - another thing I discovered was the first trainer in Misty's gym gives you a Mew, same as the Slowpoke trainer. So I got two of them instead of just one. ;D