Merfle "Green Merfle"

About

The Merfles are a species that appear in Wario Land: Shake It!. They are the residents of the Shake Dimension, living under the rule of Queen Merelda. However, when the Shake King took over the Shake Dimension, he imprisoned all but one of the Merfles inside a cage called a Merfle Barrel. The escaped Green Merfle begs Wario to help his people. Though Wario disagrees at first, the Merfle tells him that there is a great treasure that he can have if he frees them from the reign of the Shake King. Wario agrees and his adventure begins.

(Source: Super Mario Wiki)