If you happen to miss out on the star that you get from defeating the Boo's in the courtyard and getting their red coins, dont fret. You can still get 150 stars. It is simple, go to any one of the three Toads that gave you the other stars ( the one in Hazy maze Cave level entrance, near Tick tock the Clock entrance,and near tall tall mountain entrance) and talk to them, one of them will give you the star that you had missed out on earlier. This does not work for stars that you dont want to get like secret level stars on regular level stars, it only works for the Boo's courtyard star because it was a star that dissapeared near the beginning.