The Green Potion is a key item that appears in the game Paper Mario: The Thousand-Year Door.
The Green Potion is found in X-Naut Fortress and it can be found in the lab alongside the Blue Potion, the Orange Potion, and the Red Potion. During a point in the game, TEC-XX wanted Princess Peach to retrieve a special data file from Sir Grodus' room but she can only get in there by turning invisible. Princess Peach must use the four potions while following TEC's instructions. After making the invisibility potion and retrieving the file, Princess Peach can drink the Green Potion by itself to turn back visible.