Foolish Fruit

The Foolish Fruit is a treasure in  located in the Serene Shores and the Cavern for a King. It is a ripe.

Serene Shores
There is a Foolish Fruit completely buried in the northern part of the sandcastle, which is located on the southern edge of the overworld. It can only be reached from the second-highest level of the sandcastle. It can be located with the Treasure Gauge or Oatchi. To collect this treasure, you must throw 5 Pikmin in its vicinity.

Cavern for a King
There is a Foolish Fruit inside of the Horned Cannon Beetle near the north of sublevel 14 of the Cavern for a King. To collect this treasure, you must first defeat the Horned Cannon Beetle and three nearby Armored Cannon Larvae, then throw 5 Pikmin at it.