A Bub-ulb from Paper Mario: The Thousand Year Door.
In Paper Mario, four Bub-ulbs give you magical seeds which create a doorway to Flower Fields. They are found in random places in the Mushroom Kingdom.
In Paper Mario: The Thousand-Year Door there's a Bub-ulb in Petalburg that will give you a Dried Bouquet in exchange for a Hot Dog from the Glitz Pit.