The Barrel King is one of the confirmed antagonists in the upcoming PewDiePie: Legend of the Brofist game.
Not much is currently known of the antagonist itself as the game is still in development but Felix himself has played a small portion of the game on his channel and revealed that the Barrel King is at least going to be appearing as the main antagonist of the first few levels.
The Barrel King may even be the main antagonist of the entire game as the small portion Felix revealed shows that an army of anthropomorphic barrels invade his home and go on a rampage, trying to kill him and his friends under orders of the Barrel King, who seeks the power of the Brofist for himself, presumably to conquer the world. This prompts Felix (under his youtube name of PewDiePie) to go forth and rescue his fans, who the Barrel King has kidnapped as part of his plan.
- The Barrel King and his minions are the result of a long running in-joke involving barrels in PewDiePie's videos, where he often believed any barrel in a game was evil and seeking his destruction.