With Legendary Pictures producing "Pokemon: Detective Pikachu", getting the casting choices is a must if not one of many. For the legendary Pokemon, Mewtwo, many of us can agree with one choice. Benedict Cumberbatch. Just watch "Star Trek Into Darkness" and "The Hobbit" Trilogy for proof that Cumberbatch can do an amazing villain voice. He's the best choice for Mewtwo if Legendary's bringing him in "Detective Pikachu" or any possible future live-action Pokemon films.