Boneheads

Boneheads was a large, vicious skeleton-like creature that made its first and only appearance in WarioWare, Inc.: Mega Microgame$!

Story
Boneheads appears only in Kat and Ana's stage. In it, Boneheads comes in the middle of the night to possess the prince or princess of the castle. Ana appears, along with her crew of six ninjas to stop him from doing this, but all of them fail. Then, before she was captured, she sends a letter (attached to Don the Sparrow) to Kat, calling he for her help.

When Kat eventually received Ana's letter, she along with her pet Paw the Dog, immediately travel to the castle. Upon arrival Boneheads challenged her to reach the top floor, where Ana and the prince or princess was being held.

When Kat finally reached the top of the castle, she started to attack Boneheads, but she failed to defeat him though. Suddenly, Paw the Dog transformed into a giant sword that Kat eventually used to finally defeat Boneheads. He has not made another appearance since.

Triva

 * His appearance is that of a Japanese shogun.