Ribro is an antagonist and the richest person from mushroom kingdoom. He was the 2nd most rich person, but after asking Mario to steal the money from the 'early' richest person, he becomes the richest and share some of his money to Mario.
He, managed to steal all his money. It's unknown how mario did it. After the happenings, Ribro is considered a villain. He even helps SMG3 sometimes.
Ribro made several appearences, despite being evil, he appears as a good guy in Glitchy's Adventure.
In Double Kart!!, he is seen talking to Daxter. maybe daxter found out that he stole his money. He didn't appear any further in the game, but Daxter does.