Blurp

Blurps are green colored, goggle-wearing fish that sometimes appear in underwater levels alongside Cheep Cheeps, of which they seem to be relatives of due to their similar name in Japanese.

Super Mario World / Super Mario World: Super Mario Advance 2
Blurps first appear in Super Mario World, where they act as a behavioral variant for Cheep Cheeps, which in this game have only one coloration. Blurps swim endlessly in one direction, injuring Mario if one collides with him. They typically bob up and down a small bit as they swim. As Blurps are fairly weak, they can simply be defeated by shooting a fireball at them as Fire Mario or by bashing them with a cape as Cape Mario. Blurps lack pectoral fins on their sprites in this game, but have them on their artwork. They sweat while they swim, implying that swimming as fast as they do puts some amount of strain on them. They reappear in the game's reissue, Super Mario World: Super Mario Advance 2, where, like most other enemies, they can be held in Yoshi's mouth and spit out if Luigi rides him, which in their case can be used to defeat Urchins.

Super Mario Land 2: 6 Golden Coins
Blurps make a reappearance as underwater enemies in Super Mario Land 2: 6 Golden Coins. Much like their Super Mario World counterparts, Blurps aimlessly swim in one direction and can be defeated by a fireball. In this game, they occasionally pause in their swimming. Blurps are found primarily in the Turtle Zone, and also appear in Pumpkin Zone alongside statues of them and Cheep Cheeps. They again lack pectoral fins in-game, but still have them on the artwork. Additionally, their artwork depicts them as light teal with pink goggles and white lips instead of the normal grassy green with orange goggles and golden lips.

Super Mario Maker / Super Mario Maker for Nintendo 3DS / Super Mario Maker 2
Blurps reappear in Super Mario Maker and Super Mario Maker for Nintendo 3DS, replacing green Cheep Cheeps in the Super Mario World style. However, the voice heard when placing elements onto the course will still call them Cheep Cheeps. Like the other green Cheep Cheeps in the game, they swim back-and-forth a short distance while underwater, and simply hop along the bottom of the screen otherwise. Blurps reappear in Super Mario Maker 2, where they are still simply referred to as Cheep Cheeps, including in the description for the official course River Fish in the Forest.

Super Mario World television series
A single Blurp appears in the Super Mario World television series episode "Mama Luigi" where Luigi is attacked by one, but defeats it with a single stomp. The appearance of the Blurp is closer to that of a Trouter from The Super Mario Bros. Super Show!. Like its game appearance, the Blurp is green in color and has red fins, but the goggles are replaced with large white rings around yellow eyes, lacks the white on its belly, and it has four sharp teeth.

Mario & Wario
Blurps cameo in Mario & Wario as a background element of Pukupuku Kai, the sixth stage. As such, they have no interaction with any of the player characters.

Mario Party 3
In Mario Party 3, a Blurp can be seen in the scenery for Deep Blooper Sea, alongside some similar-designed Cheep Cheeps.

Mario & Luigi series
A sand-dwelling variety of Blurp known as the Sand Cheep appears in Mario & Luigi: Superstar Saga and its remake. It appears to be a normal Blurp with a fake shark fin strapped to its back. It later appears in Mario & Luigi: Partners in Time where it is thrown by Shrooba Divers.

Super Princess Peach
Like various enemies of Super Mario World, Blurps also return in Super Princess Peach. Some of them are affected by the rage vibe of the Vibe Scepter and are called Mad Blurps. They will pursue Peach if she is in front of them. They are mainly encountered in groups. In this game, they have pectoral fins, but they are depicted as being white.

Trivia

 * In Mario Mania, the names for Blurp and Cheep Cheep are swapped, which may relate to how large Cheep Cheeps were misidentified as "Blurps" in Yoshi's Story. This is also the case throughout Nintendo Power Advance V.4's coverage of Super Mario World: Super Mario Advance 2.
 * The iteration of Cheep Cheep found in Super Mario 64, known in English as "Bub," appears to be primarily visually based off Blurp, but orange instead of green. This design is additionally used in the first three Mario Party games. Super Mario 64 also introduces another eyewear-wearing fish called Bubba with a similar Japanese name to Blurp, Bakubaku.