The Pokéball Plus comes preloaded with a Mew on the ball and, to answer a question I've seen being asked, yes you can add that Mew to your party pretty much straight away. A starting team with Mew on it! Gotta love the future. You get Mew by redeeming a 'mystery gift' from the ball, and it pops out with randomly-assigned stats: there's no way to trick the game into letting you re-roll for better IVs, believe me I tried