You were playing Pokemon Red in the bus in 1997. Yes, 1997. It was a swell time, and you make it to Vermillion City In-Game, complete the SS Anne section, beat Surge handily with your Charizard, and proceed onward... but you get curious. You go back to Vermillion's dock and surf across a tile to get to the part with the truck, and you check it.

! A wild ~~M~~E~~W~~ Appeared! Holy hell, it's real! The Mew giggles... wait, it's animated!? This is Gen 1! The text box reappears. (Oh, you wanna catch me? Ha! Silly~)