Like his crewmates, Bloat is a skeleton. His voracious appetite, has caused him to grow too big, leading to his name.
Bloat is first seen where he was stuck to a wall after eating too much food and drinking too much Chuckola Cola (hence his nickname "Ostaf" ("Fatso" spelled backwards). One of the members asks Mario and Luigi to free him from the wall and the member will give up the Beanstar piece to them. They do so by blowing up the wall with dynamite and Bloat is excited to be free. However, a river of sand soon floods the ship and it eventually crashes into a large rock and sinks to the bottom of the ocean. It is unknown what happened to Bloat and the rest of the crew after this.