Question: where are the star coins in prickly goombas?
Answer: A fire breathing Piranha Plant stands to the left, so let the plant roast the prickly goomba like a popcorn kernel - or do it yourself with a fire flower. Once through the pipe, the Star Coin sits at the top of the area. To get it, open up some hidden blocks along the left or right side of the area and grab the coin.