The Big Head Potion is classified as a common potion in Adopt Me! that can be found and purchased in the Sky Castle for 10. It can also be brewed using a Big Head Cauldron in a player's house. A Big Head Cauldron costs 200 and produces 1 potion per minute.
It's currently the cheapest potion available at the Sky Castle.
The Big Head Potion allows the player to enlarge the size of their head and hat/hair. This is the only potion that does not allow the user to drink it more than once. Like other potions found in the Sky Castle, this potion's effects can be removed by resetting.