Fond memories of trying out every single glitch I could find for Pokemon Gens I and II. A lot were a load of crap, but there were a few good ones

My favorite was the Pokemon cloning glitch in Gen 2. If you did it right, you could get all 3 starters and force your rival to have the starter of your choosing. It took a couple hours to do though, because it requires not saving until you’re allowed to catch your first Pokemon. And then repeating the process.