Played through Pokémon Yellow this past week, it was easier than I remembered. I swear last time I played it after beating the Elite Four & Rival there was a place you could go to fight Ash. But this time there wasn't and I can't find anything on the internet to suggest that's the case, so now I think I might have dreamed it
Playing Fire Emblem at the moment which a friend recommended, I'm enjoying it so far.
Well as others have mentioned Red is after the Indigo League with 16 bages in Gen II.
But maybe you were thinking of Mewtwo in the Cerulean Cave in Gen I?