Oonaan is an anthropomorphic pig who lives in Octagon Village. Like his comrades Oolong and Jasmine, Oonaan is named after a type of tea, the Yunnan in this case.

When Goku, Chi-Chi and Fortuneteller Baba are in Octagon Village, Goku confuses Jasmine for Oolong. Oonaan then comes out of a house and tells Goku that neither of him or Jasmine are Oolong.

Goku then goes to search for the Bansho Fan and leaves Baba and Chi-Chi behind to stay at the Bansho Spa. Jasmine and Oonaan guide them to the spa and hide on the side of the shack peeking through a hole in the wall waiting for Chi-Chi to strip down and bath. Unfortunately, a crowd of other pigs come as well to watch and end up breaking shack causing Chi-Chi to stop undressing and panic. Chi-Chi gets mad and hits both of them making them far off in the spring.

(Source: Dragon Ball Wiki)