The inventory item meant to fix Carl's singed-off hair, per a distracted Mordecai.
When Princess Donut demands to know what is going to be done about Carl's hair — burned off entirely, an event that also earned him the Male Pattern Baldness achievement — Mordecai answers distractedly that Carl already has a hair tonic in his inventory, then wanders back toward the Crafting Room and his potions. The tonic sits alongside the Head Buffing Kit the achievement awarded him, the two representing opposite solutions to the same problem.
Carl's remedy for his burned-off hair.