Collecting all three Gold Carrots gives you something special, and there's two hidden levels. you'll need to use your mouse to find them, one is located in the forest, another in the swamp
Oooooh so that's why that one is like that, neat! Can't get the swamp one to work though, at first I thought it was because of mr man but even without visiting him it still didn't wanna click. Ah, well.
I will say the mouse mechanics seem like the only real "miss" here, just 'cause if one hand is on arrows and the other is on Z key then the mouse would require a third hand lol.