O' Berries are a fruit species. They have been seen in the wild growing on bushes, and are wild Puffles' main food source. They are the main ingredient in Puffle-O's, a popular type of Puffle Food. They have a spicy flavor, and aren't eaten by penguins. In G's Secret Mission and Questions for the Crab, O' Berries are used to complete the mission. They also make black puffles appear to be on fire.
Mission 2 - You must cheer up a black puffle by giving it an O' Berry. The puffle doesn't trust the agent until its fed one of these O' Berries. The puffle becomes his friend and helps the agent start a fire. If they do not catch a fish or you don't use the fishing pole, you can eat them.
Mission 6 - Someone tied up the O'Berries to a pine tree and the agent must use the scissors in their spy phone to get them down. They can be given to the same black puffle in Mission 2, Then Herbert traps the agent in a cage and they must throw an O' Berry onto parts of the cage so the puffle can free them.