The Compelling Cookie is a treasure in Pikmin 2 that is actually a vanilla cookie. It is located in the 3rd sublevel of the Submerged Castle. It is the 28th treasure on the List of Pikmin 2 treasures.
Captain Olimar's Journal
"My space suit's filter seems to be malfunctioning. It can't suppress the sweet, syrupy smell pervading this cavern! If I don't find a way to neutralize it fast, it's going to drive me to spoil my diet!"
"Is your palate conservative or adventuresome? Either way, this taste will ravish your mouth. For those who savor flavor, this new delicacy will have you questioning your ideas of taste."