pity

I think it's in the begining of the "a very spooky sprint" level. Go down the green mushroom ship and shoot yourself to the next platform. You shoud see bats and pumpkin goombas in front of you, and also, a shining rock at the right of the platform, what could it be? Go arroud all the platform or just jump the next level and break it. It's a launch star! Launch yourself again and you shold be in another dimension, the matter-splatter mansion! Grab the key and advance to the next room, but watch your step, it's REALLY easy to fall in this mansion. Grab the ? Coin and follow the moving floor-spot. Go into the next room and grab the key, then the ? Coin. Follow the star bit line. The next 2 keys aren't nesessary to grab but if you want to do it, it's ok. Then the last room has 4 doors. Grab the key and in the last door to open, there's a... Star bit!!!! Just kidding it's a... Coin!!!!!! Not really... It's a staaar!!!! Congratulations if you found it!!

Duetch

At the begginning a roock will be glowing and you spin it to find a launch star