Goombeetle

Goombeetles are a sub-species of Goombas that are only found in Super Mario Galaxy and its sequel Super Mario Galaxy 2. They are basically regular Goombas that wear protective helmets, which prevent them from being stomped on.

Super Mario Galaxy
Goombeetles first appear in Super Mario Galaxy. They are mostly found in Bowser's and Bowser Jr.'s galaxies. They are also found in the Buoy Base Galaxy and the Dreadnought Galaxy. They attack by charging at Mario, just like regular Goombas. However, unlike regular Goombas, they could not be defeated by being jumped on. To defeat them, Mario has to flip them over with a spin and then jump on them. Each one defeated releases a coin. If they are, however, defeated with a Bullet Bill, they will release three Star Bits.

Super Mario Galaxy 2
The Goombeetles reappear in Super Mario Galaxy 2. They act and appear the same way as they did in the previous game. They appear in Bowser Jr.'s Fiery Flotilla, Beat Block Galaxy and Chompworks Galaxy. They could also be knocked over by the Co Star Luma or could be instantly defeated by a Chomp to release 3 Star Bits.

New Super Mario Bros. 2
There will be Goombas with skulls on their heads in New Super Mario Bros. 2, and they might be Goombeetles.

Appearance
Goombeetles differ from Goombas in other ways than the fact that they wear protective helmets on top of their heads. More differences include their eyes which are not white like most other Goombas' eyes but are instead yellow-colored and just visible in the darkness of the helmet. Most Goombas also have a set of pointed fangs in their mouths but since the mouths of these Goombas are impossible to see due to the darkness, it is only assumed that they do not have those trademark fangs.

Trivia

 * They seem to be the Goomba equivalent of Buzzy Beetles, due to the similar name and the helmet they wear (which acts like a Buzzy Beetle's shell, as they protect attacks like them).