A long time ago I got a Pokémon game for a Gameboy color. It had already been used so I tested each Pokémon in battle. All was fine until I reached one strange Pokémon. When it came out in battle it was invisible, it didn't take damage from any attacks, and it's attacks had a normal amount of power. The only move I remember is teleport though there were more.
I'm pretty sure it was a hack but I wanted to make sure it was. I also want to know if it had an official name.
I restarted the game later and everything went normally, so I don't think it's a fake game.