Flavio is a 25-year old "famous" Rogueport entrepreneur. He owns many fine ships, his favorite being the S.S. Flavion, which he and Mario used to travel to Keelhaul Key. Unfortunately, the S.S. Flavion was destroyed in the very same voyage. Flavio enjoys believing that he is a fearless, brilliant man that others idolize and envy, but in reality he is not particularly popular among his crew, or anyone, as a matter of fact. He is often narcissistic and a little naïve.
Mario can first meet Flavio at Podley's bar. When talked to, he rants about his prized possession, the Skull Gem. When Mario and his friends need to get to Keelhaul Key in order to obtain the fifth Crystal Star, they decide to ask Flavio to ferry them there with his ship, the S.S. Flavion. Flavio reluctantly agrees to take Mario to Keelhaul Key under the condition that he can keep all the treasures of the pirate king Cortez. After finding an experienced helmsman to help navigate, Mario boards the ship and the group shoves off.
On the trip to Keelhaul Key, Cortez's forces attack the ship causing it to sink. The group is eventually washed ashore on Keelhaul Key and they set up camp there. Later on the island, Mario must ask Flavio for Bobbery's last request which is a Chuckola Cola. After exploring the island, Mario finds a mysterious skull rock with an opening in it. He summons Flavio to the rock and asks to borrow the Skull Gem, since it fits right into the opening in the skull rock. An entrance to Cortez's home, the Pirate's Grotto, is subsequently revealed.
Mario explores the grotto and eventually fights Cortez for the Crystal Star. However, he discovers that Cortez is immortal, and simply asks for the star, which the pirate gives to him. Mario exits the grotto and finds out that Lord Crump and his forces are bombarding the island with their ship. Flavio suggests to ask Cortez to borrow his ship, the Black Skull. After some negotiating, Cortez agrees to give Mario the ship. After a battle with the X-Nauts, Lord Crump decides to retreat, and Mario and co. go back to Rogueport.
Apparently, after the incident and bidding Mario farewell, for now, he got insurance for his boat wreck and became the second richest man in Rogueport.
Flavio was punched in the face by Zess T. after causing gourmet ingredients to spoil on the dock by holding up a crew with a two-day story. He temporarily lost his memory as a result.
Flavio is constantly bragging about how brave and courageous he is, but he is actually a coward and tries not to engage in anything dangerous, instead trying to get Mario and his crew members to do it instead. He also gets mad at anyone who disagrees with him, mainly Pa-Patch, and he either snaps at them or challenges them to a fight.
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