Octoomba

Octoombas (also referred to as Electrogoombas and Octogoombas) are enemies that first appear in Super Mario Galaxy. They are very common aliens in most galaxies, and bear resemblances to Goombas and Octopus, both of which contribute to the name. Like Shroobs, they are an alien species with a mushroom-like physique.

Super Mario Galaxy
Octoombas debut in the first mission of Super Mario Galaxy and reappear as common enemies in many subsequent galaxies. If Mario comes near one, it will try to headbutt him with its antenna. They can be defeated by spinning them or by jumping on them. Once defeated, they leave behind three Star Bits (if they were spun) or a coin (if they were jumped on). There are also two sub-species of them called Octoguys and Octopuses.

Super Mario Galaxy 2
Octoombas reappear in Super Mario Galaxy 2. They attack Mario by spitting rocks at Mario just like Octoguys. The species' name is revealed to be "Octoomba" by a Luma who guides Mario through a large planet. Two new sub-species are also introduced in the game: Elite Octoombas and Octoboos.

Super Mario 3D World
Octoombas return in Super Mario 3D World as enemies in bonus world stages, such as Super Galaxy, Gigantic Seasick Wreck, and Champion's Road. Their attack pattern has changed once again - they now spit three cannonballs (although they can be jumped on) in a straight line instead of a single rock. Octoombas are also much stronger than in the previous games, as they are resilient to almost every attack (including Rosalina's Spin attack). They can only be defeated with a Ground Pound. Octoombas are now stationary, and only rotate in position, instead of moving back and forth.

Super Mario Galaxy Trading Card description
''This class of Goomba, the long time Mario enemy, is adapted for space. These alien Goombas are found in many areas of the game and attack Mario by trying to headbutt him when he comes near. They can easily be destroyed by jumping on their heads. Electrogoombas are amphibious and have brown, red, and blue subspecies.''

Description
Octoombas have a similar physique to Goombas. Their bodies are blue with several yellow spots, and they have small snout-like mouths which they use to spit rocks. Octoombas have antennae on their heads, and three rounded feet. They use these feet to hop from side to side to move. They have sunken glowing eyes and their brows are set in a scowl. When charging up their attacks, Octoombas will glow orange.

Trivia

 * Octoombas resemble both Octoroks and Deku Scrubs from many The Legend of Zelda games. Their name is likely based on Octoroks as well.