Spawns a finite amount of Small Green Rats in batches. When it runs out of rats to spawn, it will enter a stationary state and appear angry.
When in this state, it will charge at the player if they are in proximity, breaking walls in its path (similar to Big Bandit's charge). Its charge will end in an explosion, destroying itself and releasing a final batch of Small Green Rats. The charge deals 4 damage.
- Big Rats will spawn Green Rats in bursts of 3, 4, and 5. After spawning 12 waves, they have a 75% chance to become angered in future spawn waves.
- The game code refers to this enemy as "Rat King" instead of Big Green Rat.