Koga, who encountered Red and Misty at Mt. Moon, sent Rhyhorn. His Rhyhorn used Rock Throw at the two, but Red's Pikachu repelled the rocks back to Rhyhorn. To stop them, Koga injected a substance into Rhyhorn, evolving it into a Rhydon.
Furious at what Koga did, Misty had Staryu use Water Gun on Rhydon. However, Rhydon used Horn Drill to counter the attack and redirect it to Misty, who bashed into a wall and fell unconscious. Red's Pikachu emitted electricity on Rhydon, causing it to fall down.