Bat (Super Mario Galaxy)

A bat is a Swoop-like enemy from Super Mario Galaxy and Super Mario Galaxy 2. They have pig-like noses and bulging, glowing eyes with faint rings on them, causing them to resemble Keese from the The Legend of Zelda series, particularly their incarnation from The Legend of Zelda: Twilight Princess; the two games were in development at overlapping times, so this may be intentional.

Super Mario Galaxy / Super Mario Galaxy 2
Initially, bats are found either hanging from the ceiling or flying around aimlessly. When Mario or Luigi approaches, they fly in close to him, before attempting to fly straight into him. If they succeed, they will laugh at him. They can be defeated with a spin or stomp, and they release either three Star Bits or one coin, respectively, depending on which way they are defeated. They can be found in many dark places, with the first being the cave in the Beach Bowl Galaxy. They are also found flying around the arm of Heavy Metal Mecha-Bowser. Icy locations such as the cold portion of the Freezeflame Galaxy sometimes contain an icy variant called an ice bat, which will freeze Mario or Luigi if he makes contact with it, and can be defeated only with a Fire Flower.

The Super Mario Bros. Movie
Bats appear near the castle where Luigi is captured in one of the posters for The Super Mario Bros. Movie.