I was thinking, since roughly every level has a hidden Blue Coin in it (even 4-5...), it would probably be cool to have a BlueCoin% category: Get all hidden Blue Coins as fast as possible. (This can maybe include the ones found in coin piles? Although I remember there being one of those in, for example, Morpho Knight Sword Treasure Road... It's up to any of you to include Treasure Roads or not.)

The only thing I see stopping this though, is the fact that people may have not found every Blue Coin in the game yet. I wouldn't blame them, this game is full of hidden secrets...