In Galaxy , these are often referred to as . They appear as a question mark icon on the level select screen.
There are 15 Secret Stars hidden outside the main 15 courses in Peach's Castle. You can find a comprehensive checklist on the Super Mario 64 Wiki . Secret Stars
: Enter the 1-star door on the second floor of the castle and jump into the right-hand Peach painting. In Galaxy , these are often referred to as
: In the room for Jolly Roger Bay, backflip into the small hole high in the wall to the right. Collect all 8 Red Coins underwater to get the star. Secret Stars