>>57804290That's been the term used since Gen 1 to refer to Mew kid. From the partners outside Game Freak discovering Mew was a late addition to the games, they've advertised them as "Mythical". NoA didn't bother making the distinction (to cumbersome to bother when money was there to be made) so when TPCi took over localisation, they went back and re-adjusted all the incorrect or flat-out wrong critical translations for the western market, chief among which was applying the correct term to the normally-unavailable, generally movie tie-in giveaway pokémon.
