MustBeNys is a drug that Lisa discovered.
It was created accidentally from a bunch of wildflowers found at Satan's Anvil where it fended off a large group of scorpions, making them happy. Lisa later did research on the scorpions, but Homer discovered it and gave it to a grouchy Grampa. It made him happier, but Bart made negotiations with a company to market the drug, where Grampa was the guinea pig for it. When he found the correct one, they started selling it to old people. Back at 742 Evergreen Terrace, Grampa was saying how pleased he was, but halfway through saying so, his eyeballs fell out, hanging on their optic nerves. It happened to the scorpions and all the other people who took it, causing an angry mob.