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 throws bombs. 

Knot Beret G
Knot Beret G uses a gun. 

Knot Beret S
Knot Beret S is a snowboarder Knot Beret that appears in Frost Walrus' stage. 

Shitappers
Shitappers (シタッパーズ) are enemies similar to the Knot Berets that appears in The Skiver's stage. There are blue ones that'll shoot, and yellow ones that'll throw bombs. 

Trivia

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