Tubba Blubba is the main antagonist of Chapter 3 in the first Paper Mario game. Tubba Blubba was responsible for eating many Boos.
He imprisoned Skolar, the third Star Spirit, inside his castle. He is said to be Bowser's strongest follower because Bowser made him invincible. He is often called "Invincible Tubba Blubba". If encountered in Tubba Blubba's Castle, Mario cannot defeat him and must run away. Mario soon discovered that a talking key named Yakkey unlocks the door at Windy Mill, where the secret to Tubba Blubba's invincibility lies. Yakkey woke up Tubba Blubba, however, and he chased Mario over to the doors of the castle where many Boos from a ghost town in Gusty Gulch held the doors shut on Tubba Blubba.
Mario reached the Windy Mill where he found Tubba Blubba's Heart, which was the reason for his invincibility. Mario fought Tubba's Heart, who ran away when he thought he was going to lose. He then reunited with his body, thinking it would make him stronger, but all it did was take away his invincibility and Mario easily defeated him. He gave back all the ghosts he ate and ran away crying. Afterwards, Bow revealed that he was eating the Boos as revenge for them scaring him all the time because he was such a coward.
In the credits parade (which is non-canon with the events of the game) Tubba Blubba is seen seemingly flying, but is really being carried by Boos, and Tubba's Heart is frantically chasing after his body.