Normally, Perfect Challenges are given randomly after a certain period of time. However, if you get a superb on all games (not including gatekeeper minigames or games you buy from the shop), as soon as a Perfect Challenge ends, you are given another immediately.
Easy Quiz Perfect
It's possible to earn a Perfect in the unlockable Quiz minigame by intentionally getting the first practice question incorrect.
Exchange Flow Balls for Coins
Usually, Flow Balls unlock Rhythm Games from the shop. However, if you've already bought all the shop games, you will automatically receive 30 coins for each extra Flow Ball in your possession by talking to Saffron.
Mascots
While you are playing the game, you may notice Tibby in the bottom-right corner of the screen when the game is loading. However, you can obtain mascots to replace Tibby in the loading screens by feeding your goat to certain levels, every ten levels, up too 200.
Complete all the challenges in Saffron World and Saltwater World (you do not have to do the 'Super Hard!' Challenges). Tread Carefully! Paprika World is no joke.
Wario... Where?
Complete all challenges in Paprika World (excluding the Super Hard ones).
Constant Perfect Challenges...