Wild Wilbur used to be an outlaw. He stashed his loot in a cave, which was found by Ryder, Rubble, Everest, and Chase. Mayor Humdinger was also looking for his loot. His loot consisted of two chests, one with gold and silver coins, and the other full of long-johns (long underwear).
Not much is known about Wilbur's personality, other than the fact he was a successful and notorious wild west outlaw. It was suggested by Ryder that in addition to stolen treasure like silver and gold, Wild Wilber also viewed long-johns as treasure due to storing them along with his loot as warm clothing would be valuable and necessary to the survival of someone living in the cold mountains. This also shows that Wilbur was at least practical and had enough common sense to know how important something as simple as long-johns would be to both his survival and comfort on mountains during winter. Given the amount loot he left behind, he was shown to be a successful and competent outlaw. He was also to have enough knowledge of the mountains near his cabin, to hide his treasure away without it being found until many years after his death. He also was shown to quite cautious, as he hide the treasure map containing his loot's in his cabin.
Wild Wilbur's appearance is a mystery as he is only mentioned in "Pups Save an Outlaw's Loot" and no painting or photograph of him is shown.