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 is captured, Ana sends a letter (attached to Don the Sparrow) to Kat, calling for her help.
When Kat eventually receives Ana's letter, she, along with her pet Paw the Dog, immediately travel to the castle. Upon arrival, Boneheads challenges her to reach the top floor, where Ana and the prince or princess are being held.
When Kat finally reaches the top of the castle, she starts to attack Boneheads, but she fails to defeat him. Suddenly, Paw the Dog transforms into a giant sword that Kat eventually uses to finally defeat Boneheads and save the others. While not reappearing in the game itself, he has a quick cameo in Kat & Ana's character trailer for WarioWare Gold.
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