When Team Rocket, hired by Nastina, wanted to eliminate Tentacool, they used a special liquid, but they saw there were just too many Tentacool. One attacked the barrel and the liquid was spilled onto it. Tentacool evolved into a Tentacruel, but a hundred times bigger. It became the Tentacool's leader and attacked the city. Fortunately, Misty was able to persuade it and Tentacruel went to the sea.