A Super Star is an item found throughout the Yoshi series. It is a Cape shaped like a Star and possesses the powers of both the Starman and the Cape Feather. When donned, Baby Mario is granted great power, Yoshi transforms into a large Yoshi Egg and Baby Mario is invincible to enemies and hazards, can run up walls and ceilings, and can glide with his new cape.
Super Mario World 2: Yoshi's Island/Yoshi's Island: Super Mario Advance 3
The Super Star makes it's debut in Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3. When donned, Yoshi becomes a giant Yoshi Egg and Baby Mario dons a Cape and can glide, and run up walls and ceilings. Additionally, he is invincible and can defeat basically any enemy and cannot be killed by spikes. The effects are only temporary and will wear off after some time. The Power-Up debuts in World 2 and makes infrequent appearances from there.
Yoshi's Island DS
The Super Star is back in Yoshi's Island DS with the same effects as before. It debuts in Baby Mario and Baby Peach: Dynamic Duo! and once again grants Baby Mario the ability to glide and run up walls all while being invincible and Yoshi becoming a large Yoshi Egg. It is much less common in this game in fact the next time it is seen is at the end of World 4. In this game, only Baby Mario can obtain a Super Star, if Yoshi is carrying any other Babies, he won't be able to obtain a Super Star.
Yoshi's New Island
The Super Star returns in Yoshi's New Island however it has changed in this game in comparison to it's previous appearances. It no longer bounces around and instead remains in place in the air. When Yoshi grabs the Super Star, instead of Baby Mario taking control, Yoshi is granted the ability of super fast running so fast that he can run up walls and ceilings, additionally, he can also flutter greater distances. Just as before, it is an uncommon power-up. A similar item called the Rocket Star also appears in this game.