London, England
A scientist frantically came into the lab, holding a laptop. "Guys!" He seemed out of breath. "Guys, we have a problem."
"What is it?" one of the scientists in the room asked.
"It's..." He paused to catch his breath. "It's the Pokémon universe. Something has already gone wrong." He set the laptop on the corner of a desk and flipped through a few of the many windows he had up. "The instruments have gone mad! It might just be my computer, but I swear something's off." All of a sudden, a shadow came over the computer. The scientist looked behind him, and in the few seconds he had, he recognized the figure. It was the famed rogue Pokémon. Mewtwo.
Now, if you didn't get the gist of it from there, basically something's gone wrong in the world of Pokémon and the Pokémon are starting to come into the real world. Although, just how that happened, you'll have to find out for yourselves.