Merfle

The Merfles are a species that first appeared in Wario Land: Shake It! for the Nintendo Wii. They are the residents of the Shake Dimension and 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 free Merfle begs Wario to help his people. Though Wario disagreed at first, the Merfle told 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.

Role in Wario Land: Shake It!
The Merfles are the creatures that Wario has to rescue in each level of the Wario Land: Shake It! game. They are usually found near the end of the level in a tough cage made by the Shake King himself. To free the Merfles, Wario must grab the cage and shake it in order for it to collapse, thus freeing them. In most cases, they also act as guides after that to help Wario race back to the said level's entrance before the timer hits zero.