Porcupuffer

Porcu-Puffers (also spelled as Porcupuffers) are a species of Cheep-Cheeps that first debuted in Super Mario World. They resemble giant blue-purple Cheep-Cheeps with big red lips and blue spikes all over their backs.

Super Mario World
Porcu-Puffers appear in Super Mario World, where they follow Mario and Luigi in the water. The Mario Bros. can perform the Spin Jump on them to "ride" them, or use Yoshi. They appear in three levels, the secret level on top of the Vanilla Dome, and a secret area in the Cookie Mountain level. They also appear in a hidden area from Chocolate Island 1.

Super Mario Galaxy
After a long hiatus, this enemy reappears in the game Super Mario Galaxy. However, only one appears, and it is in Drip Drop Galaxy. The Porcu-Puffer is hidden in an underwater chest.

New Super Mario Bros. Wii
Porcu-Puffers are featured again in New Super Mario Bros. Wii. Here, they attack exactly the same as Spike Bass in the DS game, lying near the surface to pursue the plumber and his party or even leaping from the water to attack. Porcu-Puffers serve as obstacles for World 4, and they appear again in World 6 in level 6-5 and later in World 9 in level 9-2. They can only be defeated with a fireball, star or koopa shell. They can also be frozen, but they crack out almost instantly, much like a Spiny Cheep-Cheep. In most cases, and not in the obstacle course, Porcu-Puffers come infinetly, but still one by one, to the player. For example, if a Porcu-Puffer is defeated by the player, another one will come to take its place.

Super Mario Galaxy 2
Another appearance is in Super Mario Galaxy 2. Like the prequel, they are very rare. They only appear in Cosmic Cove Galaxy.

Super Mario 3D Land
Porcu-Puffers later appear in Super Mario 3D Land, inhabiting underwater and beach levels. They retain their appearance from New Super Mario Bros. Wii. In World 6-1, Porcu-Puffers jump out of waterfalls, attempting to hurt Mario, and may even break some portions of the bridge he uses to reach the end of the level.

Mario and Sonic at the London 2012 Olympic Games
Porcu-Puffers also appear in Mario and Sonic at the London 2012 Olympic Games. During the Dream Rafting event, the second task a team is required to do is defeat them. To defeat these Porcu-Puffers, the participants must Ground Pound the raft at the same time when they're beneath it. They also appear during the Highway Tally game in London Party mode.

Mario & Luigi: Superstar Saga
A similar species called Puffer-Cheeps appear in Mario & Luigi: Superstar Saga.

Trivia

 * Porcu-Puffer is a portmanteau of 'porcupine' and 'puffer' (puffer fish).
 * In both Super Mario Galaxy and Super Mario Galaxy 2, the Porcu-Puffers somehow disappear after a short while. This makes their status as a rare enemy even more rare, being momentary.