Peppermint Butler's eye after a drop accidentily fell on it
 
The spicy potions are brews concocted byPrincess Bubblegum to eliminate the users need to shower by having the drinker sweat cleansing agents. Because Finn doesn't bathe he was prompted to test it for Princess Bubblegum in "Too Young", however, it turned out to be incredibly spicy. Later in the episode, Princess Bubblegum made a second batch that was even spicier than the previous bottle that Finn drank to help him prank theEarl of Lemongrab by trying to spice all of the Earl's food.