Ash and the group came by and unsuccessfully stopped Team Rocket from getting away with Gyarados, and they too got captured by Team Rocket. Professor Sebastian explained to them that the red Gyarados was forcibly evolved from a normal-colored Magikarp. Since it didn't have time to officially complete the evolution, the coloration of the Pokémon ended up staying red instead of turning blue.
Gyarados on a rampage
During Rage of Innocence, after Team Rocket's success in catching the red Gyarados, they decided to do some research on it. Meanwhile, Lance found out that the Evolution Inducement Ray was the cause of all the unevolved Pokémon growing tired. He then destroyed its source with the help of his Dragonite's Hyper Beam. After the machine was destroyed, all of the side effects it caused disappeared. No longer affected by the ray, the red Gyarados began to go on a rampage. It then escaped from the helicopters Team Rocket was carrying it in and dove into the water below. The red Gyarados continued its rampage, destroying everything in sight with Hyper Beam. Ash tried to stop it from going berserk, but it had no effect, making Gyarados retaliate with Hydro Pump.
The Team Rocket grunts tried catching it with another net. This time, Ash sent out Bayleef to cut the net with Razor Leaf. Just when the grunts were defeated, the Team Rocket trio arrived and shot a different net at the red Gyarados. Gyarados broke free from the net and went on another rampage, moving towards the river in Mahogany Town. Pryce stopped the Atrocious Pokémon from going any further by having his Dewgong use Ice Beam on the river. Lance, after defeating Tyson, battled the red Gyarados with his Dragonite in order for it to calm down. Lance successfully did so and caught the red Gyarados.
Shortly after capturing Gyarados, Lance promises Ash that he will take care of his new Pokémon and that, like Dragonite, he will be his friend. The Red Gyarados reappeared in a flashback in Beauty is Skin Deep, when Ash and his friends told Clair about what happened in Mahogany Town.
In Gaining Groudon, May, Max, and Brock rode on Gyarados when Ash was captured by Team Magma, Brock recognized the Atrocious Pokémon almost immediately. After the confusion is over, and Brock explains who Gyarados belonged to, he takes the trio to the island where Ash, Pikachu, and Lance meet. This time, Gyarados is more calm and loyal to its Trainer's order, showing that Lance managed to fulfill his promise to care for the Pokémon.
Prior to Lance capturing the red Gyarados, it had a bad temper towards people. It became worse after the machine forcing Pokémon to evolve got destroyed. Because of the increased rage, Gyarados easily broke out of the prisons Team Rocket held it in. After Lance caught Gyarados, it calmed down. During Pokémon the Series: Ruby and Sapphire, Gyarados got along with people and worked with Ash's friends to help them out during the fight with Groudon and Kyogre.
Gyarados evolved from a Magikarp sometime before the events of the manga. It debuts in Extricated from Exeggutor together with Lance's other Pokémon. Later was used to shield Lance from the lava on Cerise Island using its bubbles.
It is later used in the final battle against Yellow alongside Lance's Dragon Pokémon.
Gyarados was the first test that Red and the gang had to handle. It popped out of a pool of water when Lance commanded it to do so. Gyarados was proven to be a challenge when it kept on hiding in the water and used its tail at one point to slap Clefairy. Clefairy tied Red's Pikachu to a fishing line and threw him to the pool of water to find Gyarados. After Pikachu went inside Gyarados's mouth, Pikachu shocked it, defeating Gyarados.
Lance's Pokémon Cards listed with a blue background are only legal to use in the current Expanded format. Cards listed with a silver background are legal to use in both the current Standard and Expanded formats.