The Biggest Problem With Mewtwo's Return In Pokémon
If there's one thing "Pokémon Journeys" excels at, it's making a good callback. In many ways, this iteration of the "Pokémon" anime serves as the ultimate celebration of longtime protagonist Ash Ketchum's 25-plus-years' worth of adventures. He travels across each of the series' distinct regions, reunites with old friends, and finally becomes the very best (like no one ever was) by becoming the Pokémon World Champion. Notably, the series also follows up with certain characters that had been absent from the anime for many years, and one of them, in particular, is no doubt recognizable to longtime fans.
"Pokémon" fans may recall 1998's "Pokémon: The First Movie" for being the first time the franchise made it to the silver screen and being the anime introduction of the ultra-powerful clone Pokémon Mewtwo. Mewtwo proved to be a memorable antagonist, with philosophical musings about life's meaning, giving him a surprisingly complex character arc. Though it had been roughly 20 years since Mewtwo last appeared in the anime, "Pokémon Journeys" finally heralded the reunion between the hyper-intelligent Pokémon and Ash. Unfortunately, there's a bit of a glaring issue when it comes to Mewtwo's big anime return.
There's two Mewtwo now
The thing about Mewtwo's return in "Pokémon Journeys" is that, while the character hadn't appeared in the mainline anime for many years, the same wasn't accurate for its species. In truth, there was a point where the series introduced an entirely different Mewtwo from the one first seen in "Pokémon: The First Movie" — and, yes, it's just as continuity-bending as it sounds.
2013's "Pokémon the Movie: Genesect and the Legend Awakened" actually saw Ash and friends encounter an entirely new Mewtwo — one that can also talk and has a similar origin to the original Mewtwo, but who is nevertheless a different character. This creative decision came about as a result of a rights issue, as the writer of "Pokémon: The First Movie," Takeshi Shudo, retained the rights to the original iteration of Mewtwo and didn't sign off on the team's desire to reuse that specific character for the movie (via The Gamer).
Ultimately, having two separate Mewtwo is a bit of a plot hole, considering how it's supposed to be one of the rarest Pokémon. Of course, such a discrepancy could be ignored if the original Mewtwo was eventually retconned out of continuity ("Pokémon" has always played fast and loose with canon), but the character's eventual reappearance in "Pokémon Journeys" and the explicit confirmation that it's the same Mewtwo from the first movie (via Comic Book) definitely complicates things.