Pokémon: The First Movie is the reason Mewtwo is in Detective Pikachu - Polygon

Pokémon: The First Movie: Mewtwo Strikes Back arrived in 1998. More than 20 years later, the story of Ash, Pikachu, Mew, and Mewtwo has new resonance as the Pokémon come to live in live-action while keeping Pokémon game and anime canon alive.

Mewtwo destroys the Lab Pokémon: Detective Pikachu Opening Scene

Mewtwo in 'Detective Pikachu' Could Mean Big Things for a Pokémon Movie Universe

New Pokemon Movie 'Mewtwo Strikes Back Evolution' Debuts First Trailer - Heroic Hollywood

Detective Pikachu' - Review Thread : r/movies

Detective Pikachu Ties Directly Into Pokémon Red & Blue - Here's How

Pokémon Detective Pikachu Director on How Mewtwo Connects to Kanto - IGN

Why Mr. Mime Was Almost Cut From Pokemon: Detective Pikachu - IGN First - IGN

The Stunning Transformation Of Pokemon

Detective Pikachu director: twist ending didn't need post-credit scene - Polygon

Mewtwo (Detective Pikachu 12) - Bulbapedia, the community-driven Pokémon encyclopedia

Pokémon Detective Pikachu Director on How Mewtwo Connects to Kanto - IGN

Where Are The PokeBattles In Detective Pikachu?