Nintendo's Mario Tennis Open for the Nintendo 3DS may not be as packed with Mushroom Kingdom whimsy as its predecessors, but it's still a compelling little game. Plenty of playable characters such as Mario, Luigi, Princess Peach, Bowser, and the rest of the traditional gang take to the courts, but Nintendo has included a few extra unlockable characters that must be activated with secret QR codes. The company has been releasing these codes one at a time over several weeks, but now someone over at Reddit has compiled them all into a single image for your convenience. Just load up the North American version of the game (other regions use different codes) and press Up and Start on the data file select screen. That'll trigger the secret camera function. Use the camera to scan the QR codes one at a time to unlock a rainbow of Yoshis, Metal Mario, and a special Yoshi costume for your Mii. It's a fun way to unlock new content despite the heavy reliance on Yoshi. At least the dinosaurs are all skilled in different tennis disciplines!