Silver Stars are items appearing in the Mario series as types of Stars. They first appear in Super Mario 64 DS and return in Super Mario Galaxy and Super Mario Galaxy 2. In all of the games that they are present, Mario (or any other playable character) must collect five of these Stars in some levels to form a Power Star. According to a Honeybee in Super Mario Galaxy 2, the five Silver Stars fall from the sky.
Super Mario 64 DS
Silver Stars are introduced in Super Mario 64 DS, being a new feature introduced into the game from the original game. In some levels, the player must collect five of them to get a Power Star that will appear inside a Star Sphere. They are found in several courses, including Battle Fort and Sunshine Isles. If a character gets damaged while holding one or more Silver Stars, he will lose one and it will scatter and bounce around the area nonstop. The player must catch it again to retrieve it. If the player has all 5 Silver Stars and then drops one, the Star in the Sphere will disappear, like if a Switch Star is pressed and is not collected in time. The touch screen shows the location of these stars. Silver Stars can only be collected if the Silver Stars mission is chosen from the menu.
Similar physics are used in the multiplayer mode of Super Mario 64 DS and the missions may have been the inspiration of the multiplayer mode or the other way around. However, in multiplayer mode, the Silver Stars are replaced by Power Stars.
Silver Stars reappear in Super Mario Galaxy having the same role as in Super Mario 64 DS. This time, they float in Bubbles, and the player will not lose one if they manage to take damage. The Stars also float around Mario, unlike in Super Mario 64 DS where they "disappear" after being collected. When all 5 Silver Stars are collected, a cutscene shows the five Silver Stars merging into a Power Star.