Cheep-Cheep

Cheep-Cheeps are fish that made their first appearance in Super Mario Bros. in the underwater levels, just like Bloopers. They are pretty annoying, but can be taken out with a fireball. In some levels Cheep-Cheeps jump off from the bottom of the screen creating random obstacles. In Super Mario Bros. 3 they act the same but can also jump out of water and lava. Cheep-Cheeps are also found in many Mario Kart courses. Although they were not included in the credits in Super Mario World, they posed a numerous threat as the white, slow-moving fish found underwater and in floating bubbles. Super Mario Land: 6 Golden Coins again featured Cheep-Cheeps. Cheep-Cheeps impeded Mario's progress through the Macro and Turtle Zones by swimming back and forth in the water, like a Goomba. Among the other fish, they were accompanied by similar-looking Blurps. They could be destroyed by a tossed Green Shell or a fireball.

In the Paper Mario series, Cheep-Cheeps are considerably more intelligent than their predecessors, and are able to speak, as well as, strangely enough, safely live and travel about on land. As indicated in Paper Mario: The Thousand-Year Door, many even have jobs, such as blimp conductor and chef. Most significant of these land-dwelling fishes is Sushie, a female Cheep-Cheep who was among Mario's many partners in Paper Mario. They are found in Super Mario Sunshine as well, in places with water, like Ricco Harbor and Noki Bay. Even though most of the time they are flailing out of water, they cause you to spin out when touching them. They can be defeated with FLUDD, but will reappear almost instantly. Yoshis can turn them into platforms by spraying them with certain fruit juice. It is theorized that the land-dwelling Cheep-Cheeps are a subspecies, or possibly a separate species, from the aquatic, non-speaking Cheep-Cheeps. Cheep-Cheeps have also appeared in the Mario Party Series.

Language
According to Paper Mario: The Thousand Year Door, Cheep-Cheeps have there own language, which is also called "Cheep-Cheep". This language is presumably spoken natively by Cheep Cheeps, and it is only partly heard through the character Chef Shimi (who often mixes words, such as "saved" and "shaved", up due to his unique language knowledge). However, in Paper Mario, the letter Sashimie wrote to Sushie is not written in any special language.

Trivia

 * Just like in the Real World humans usually say "Cheese" when they're getting a picture taken, in the Mushroom Planet characters instead say "Cheep-Cheep". This was proven true in Mario & Luigi: Superstar Saga.