Knot Beret

Knot Beret (ノットベレー) is an enemy from Mega Man X4. There is a modified version of it in Mega Man X5 called Shitappers. They are the short, fat enemies that are the basic soldiers of Repliforce that appear in certain stages. 

Knot Beret B
Knot Beret B is an enemy that appears in the first part of the Sky Lagoon Stage, Slash Beast's train stage and Spaceport stage in Mega Man X4. They attack by throwing bombs. The "B" in the name could stand for their usage of bombs, or just for their bronze brown color scheme. 

Knot Beret G
Knot Beret G is an enemy that appears in the first part of the Sky Lagoon Stage, Slash Beast's train stage and Spaceport stage in Mega Man X4. They attack by shooting with their pistols. The "G" in the name could stand for their usage of guns, or just for their olive green color scheme. 

Knot Beret S
Knot Beret S is an enemy that appears in the first part of the Frost Walrus' stage. They can only attack with contact damage while sliding on snow platforms. They can be a nuisance since they can throw X or Zero to a row of ice spikes below the snow platforms or delay their movement, giving time to the snow platform to crumble and send them to the ice spikes as well. The "S" in the name could stand for their usage of snowboards, or just for being deployed on Snow areas. 

Shitappers
Shitappers (シタッパーズ) are enemies similar to the Knot Berets that appear in Spiral Pegasus' stage. There are blue ones which attack by shooting, and yellow ones which attack by throwing bombs. 

Other Media
Knot Beret Gs and Bs appear in the Rockman X (manga) defending Slash Beast's train alongside Batton Bone B81s and a Raiden.

Trivia

 * Shitappers is the same Japanese name of the Birdbots from the Mega Man Legends series, which can be translated as "underling".