From the Super Mario Wiki
Octoguys also known as Octo Guys are recurring enemies appearing in the game Super Mario Galaxy and Super Mario Galaxy 2. They resemble red Octoombas with lighter pink spots. They are different from other Octoombas because they can spit rocks upwards.
Octoguys are one the most difficult and resilent in these games so items like Life Mushrooms should be eqquiped. There are two reason why Octoguys are very hard to kill. The first reason why Octoguys are resilent is because an Octoguy's rock is much faster than an Octoomba and unlike their weaker cousins, Octoguys will chase Mario. The second reason is when they are near a cliff, Mario may fall off the ledge and possibly lose a life. What's even worse that makes it more frustrating for the player is because Octoguys will back away when Mario is near them to dodge every attack that Mario attempts, however, they will eventually become tired and they will stop running to catch their breath. This gives Mario an easier attempt to defeat them though Octoguys do not get tired for long at all. Mario must quickly slay them after when they attack. A Star Bit can be used againest an Octoguy leaving it defenseless. Humorously if Mario used a Ground Pound on them, it will be flat as a pancake. The easiest and proper way to kill Octoguys is by Spining them or shooting a Star Bit then stomps while Jumping on them without using Star Bits can be hard. Like most enemies, they drop a Coin or 3 Star Bits by jumps or Spining them respectivly.
Super Mario Galaxy
In Super Mario Galaxy, they are semi-common enemies appearing in mass numbers in the Honeyhive Galaxy, Buoy Base Galaxy, Gold Leaf Galaxy, and Deep Dark Galaxy. Octoguys are smart, but not very smart as they lose Mario if he is out of sight, or if he is behind them. In the Honeyhive Galaxy, Octoguys appear in the water-filled planet, trying to prevent Bee Mario from getting to the Queen Bee. They also appear on the Queen Bee's planet. Two of them appear on the fortress in the Buoy Base Galaxy. In the Gold Leaf Galaxy, they appear in the final planet of the second mission in the water-filled section. In the Deep Dark Galaxy, they guard a Fire Flower that is needed for Mario or Luigi to proceed through the level. A lone Octoguy also appears in "Bubble Blastoff", trying to knock Mario off a pole he is climbing.
Super Mario Galaxy 2
In Super Mario Galaxy 2, Octoguys return. They appear in the Boulder Bowl Galaxy, in the Honeyhop Galaxy and Shiverburn Galaxy's Prankster Comet mission. One of the easiest ways to take out these annoying little creatures thanks to the help of a Rock Mushroom is with Rock Mario while Boulders also crush them since Octoguys come in high packs. They have not changed much from their previous game.
Names in other languages