Sarah wrote some notes... as in potions she actually took notes. She thought about the ingreidient of similar potions .... the buffdlement potion for example, perhaps scurvy grass then. No, perhaps something smelly. Then she had it. She raised her hand, "what about blue cheese that smells awfully bad? Perfectly gaggable!". It smelt like smelly socks or her brothers after they had done a lot of running around outside.