As Nintendo details, add $50 or more in funds to your Wii U eShop accounts between now and midnight PT on July 28 (3AM, July 29 ET) and you'll get an extra $5 in credit, but if you add over $100 in funds then the reward goes up to $10. Lovely! You won't have long to wait for the e-dough either, as Nintendo promises delivery of the bonus dosh by August 2.
Nintendo helpfully suggests some of the upcoming big names you could spend the extra credit on, including Pikmin 3, The Wonderful 101, and Rayman Legends. We say don't forget about the less big-name come-and-gones like Toki Tori 2, Runner 2, and Little Inferno, or else the cute little kitten gets it*.
*That's our actual real-life Kirby kitten, so in all honesty he's probably safe