Cheep Cheep

Cheep-Cheep is a common fish species of the Mushroom Kingdom, first introduced in Super Mario Bros., where it appears as a common underwater enemies. This foe lazily swims forward or leaps out of the water and soar through the air from Super Mario Bros. 3 and onward. As a species of fish, it lacks complex free-will, thus Bowser is able to cultivate them and use them as his minions.

Cheep-Cheep can survive out of water, though its means of locomotion on it varies between games, either showing it flopping around uselessly or hopping from place to place. Throughout its appearances, the attack pattern of Cheep-Cheep remains consistent, slowly swimming towards the player, although Sushie, a purple Cheep-Cheep and ally of Mario, is shown to be capable of such feats as belly flopping and manipulating water.

Mario Kart series
In the Mario Kart series, Cheep-Cheeps most commonly appear as background scenery or obstacles and rarely have a more active role in the games. They are different colored and are sometimes in the water, sometimes on the sand on the track. Cheep Cheep Beach from Mario Kart DS, Cheep Cheep Island from Mario Kart: Super Circuit, and Cheep Cheep Lagoon from Mario Kart 7 are named after them.

Super Mario Galaxy
Cheep-Cheeps appear also in this game, and especially in the Deep Dark Galaxy's third star, before the planet with tennis balls inside. They hurt Mario if touched, and they bounce for moving, making them hard to kill. They also bother the player by disfocusing him.

Other Media
Cheep Cheeps are absent from most derivative Mario mediums such as cartoons and literature, but one does appear in the anime film Super Mario Bros.: Peach-Hime Kyushutsu Dai Sakusen!