Tubba Blubba became invincible when his heart was removed by Bowser. Hiding the heart in the Windy Mill, it controlled Tubba like he was a puppet. However, Mario discovered the hairy heart, and the two battled. It is one half of Chapter 3's boss.
Tubba's Heart may have been inspired by Sluggy the Unshaven, a boss who also had a hairy heart as a weakspot.