Oolong is a pig who attains the ability to shapeshift. He first met Goku and Bulma on their quest to gather all of the Dragon Balls. Oolong along with Puar both attended a shapeshifting academy in which he bullied him. After completing school Oolong began to live in a formidable mansion next to Aru Village. He was able to acquire his wealth through ripping off the nearby villagers and kidnapping the women, who were fairly ok with the process, due to the fact they were able to live a life of luxury. Although Oolong quits his kidnapping ways after being stopped by Goku and decides to accompany he and Bulma.
Oolong wearing the pair of underwear he wished for
After being trapped by Emperor Pilaf, Oolong and Puar are able to escape through the hole created by Goku's Kamehameha Wave, by transforming into bats. Before Pilaf is able to grant his wish, Oolong is able to stop him in his tracks by shouting to Shenron he wishes for a pair of underwear. After the conclusion of Dragon Ball Oolongs role is significantly reduced, similar to that of Puar's. Although he continues to support the Z-Fighters in their efforts to save the world. In Dragon Ball GT, Oolongs role becomes completely obsolete and is shown only a few times. Alhough, we do learn that his wish for the underwear is responsible for the creation of Oceanus Shenron.