Monstro is an early boss in The Binding of Isaac, the indie roguelike dungeon crawler first released in 2011, where players fight through randomly generated rooms as Isaac. His distinctive blarg has circulated mainly through gameplay clips, streams and fan soundboards, where short boss noises are easy to lift and reuse. Because the game has stayed popular through remakes and expansions, and because the sound is so short and recognisable, it keeps showing up in Isaac edits, reaction videos and gaming memes long after players first met the boss.