This earth-shattering crossover is a collaboration between The Pokémon Company and Nintendo for a new limited edition line of merchandise that includes keychains, playing cards, notebooks, and T-shirts. Unfortunately, as far as we can tell, these items are only available in Pokémon Centre stores in Japan from October 29th. You'll have to be very lucky on eBay to get any in the West.
Now I'd be lying if I said I couldn't quite put my finger on why Mario Pikachu is so good because — honestly — it's the mustache. It's obviously the mustache. In fact, Pikachu looks so good with a mustache I'm wondering why the original character design didn't feature one in the first place. It's elegant. Dignified. And just imagine the little fella saying "pika" with a soup strainer like that. I'm just hoping someone gives Pikachu mutton chops next.