He is a baby jabbi in Paper Mario The Thousand Year Door. He is found in the item shop behind a tree stump. You can ether make him join your puni party, or scare him away! He is a really minor character in this game. After you beat the chapter you can find him again. Go to the room next to the red and blue cages, then kick all the bushes. He will pop out of one and give you a mushroom. The puni count still says 101 if he joins you. He and Punio used to be best friends, then he thought Jabble joined the X-nauts. It is proved that he didn't if you found him in the secret item shop.
All the punis following you could be a resemblance to pikmin following Olimar.