Cilan and Brock! Gyarados' Outrage!! (デントとタケシ！ギャラドスのげきりん！！) is a bonus episode special as well as the 21st episode of Pokémon: Best Wishes! Season 2: Decolore Adventure and the 46th episode of Pokémon: BW Adventures in Unova and Beyond.
Coming to Johto, Cilan comes to a lake and goes to fish out a Qwilfish, but instead encounters a Gyarados. During the battle, Gyarados damages Pansage and gets affected by a strange light. Cilan runs off to leave Pansage to be healed by Nurse Joy, but a friend of his friend comes to heal Pansage and help Cilan to stop Gyarados, who is outraging.
In a forest of Johto region, Cilan and Pansage try to find their way out, but got lost. They go back and encounter a lake. Cilan is pleased to find this place and finds a Qwilfish swimming in the lake. He decides, as a Fishing Connoisseur, to catch this Qwilfish. Cilan casts his lure and the Qwilfish dives in. Cilan tries to pull Qwilfish out, but it is too strong for Cilan, so he gets help from Pansage. However, Cilan and Pansage are shocked that the fished out Pokémon is actually a Gyarados. Cilan admits this Gyarados is of high quality he fished out. Gyarados spits out the lure and uses Hydro Pump, chasing Pansage and Cilan away. Pansage uses Bullet Seed, hitting Gyarados, followed with Rock Tomb. Pansage jumps and goes to use Solar Beam, but Gyarados retaliates with a Flamethrower.
Cilan won't give up in catching Gyarados, but sees Gyarados being electrocuted by something. Gyarados uses Hyper Beam, damaging a part of the environment, revealing a man. Gyarados dives in and swims away. Cilan runs to heal Pansage in a Pokémon Center, but is watched by a man. Cilan runs off and nearly bumps into Brock. The two boys apologize for nearly bumping into each other. Cilan runs off, while Brock is troubled. Cilan gives Nurse Joy his Pansage for healing, though Nurse Joy thinks it must've been the Gyarados that attacked them. Brock comes back and asks if he could heal Pansage. Brock admits he is a student to become a Pokémon Doctor and was sent here to assist another doctor. Nurse Joy permits him and Brock puts on his lab coat. Brock and Nurse Joy go to the operating room, while Cilan waits. After a while, Nurse Joy returns and promises Pansage will be fine as long as Pansage gets his rest.
Nurse Joy asks Cilan how did he encounter Gyarados. Cilan admits he fished it out and battled Gyarados. Nurse Joy lets him know Gyarados is supposed to be the master of the lake and if a Hyper Beam was fired out, there would've been trouble. Cilan remembers Gyarados did fire out Hyper Beam before its body started glowing. Nurse Joy replies she never heard of that phenomena. Brock returns, telling he is done. Nurse Joy and Cilan thank him for healing Pansage. Nurse Joy thinks he will be quite the doctor. Brock still considers him inexperienced in that matter, but an expert when it comes to flirting, claiming he will do his best to become a doctor for Nurse Joy. However, he gets hit by his Croagunk's Poison Jab and gets dragged off. Nurse Joy gets another patient with a Pikachu. Cilan and Brock were surprised a bit, thinking "they" couldn't be here. The girl, Ayumi, reports her Pikachu cannot use Thunderbolt. Brock and Cilan examine her, but find nothing strange with Pikachu.
Cilan admits he is a Connoisseur. Ayumi tells her Pikachu learned Thunderbolt a week ago, so Cilan feeds Pikachu with special Pokémon food. Brock eats part of the food, seeing Cilan was wise to mix berries. Pikachu is fed, so Cilan suspects she is just untrained, as Pikachu needs time to master the attack, volunteering to help her out. Outside, Pikachu goes to use Thunderbolt on Stunfisk, but fails. Per Cilan's advice, Ayumi and Pikachu take deep breaths before launching an attack. Repeating the attack, Pikachu succeeds in hitting Stunfisk. Brock has no doubts in Cilan's skill as a Connoisseur. Seeing Stunfisk and Pansage, Brock thinks Cilan is from Unova. Cilan confirms this, wanting to train more as a Connoisseur, so Brock decides to cook for both of them. Brock managed to prepare food for Ayumi, Cilan and their Pokémon. Brock admits it has been some time since he cooked for others, remembering the time he traveled with his friends. Cilan admits he also did the same, wondering how are they doing today.
Suddenly, they hear some trainers, whose Pokémon got injured by a Gyarados. As Nurse Joy goes to heal these Pokémon, Cilan decides to accompany Ayumi home, while Brock goes to face Gyarados. As Gyarados is attacking, the townsfolk retreat, with Officer Jenny ordering to stay off the river. Growlithe uses Flamethrower, but it and Officer Jenny are hit by Hydro Pump from Gyarados. While Jenny is tracking Gyarados, the man appears, picking up the Qwilfish robot, as he didn't expect Gyarados to go on a rampage. As Gyarados moves away, Jenny blocks its path so it cannot return back. Cilan tries to stop Gyarados, as his actions caused it to go on the rampage. Gyarados uses Flamethrower, but is countered by Growlithe's own Flamethrower. Gyarados dives into the river. In the Center, Officer Jenny, Nurse Joy, Brock and Cilan agree they have to return Gyarados back to its lake. Cilan thinks to achieve that, he can pull it using his own rod. As they watch the injured Pokémon, Brock promises to return Cilan his Pansage after the crisis is resolved.
Cilan throws his lure into the river, allowing Gyarados to go back up. However, Jenny casts a net to capture Gyarados and starts the boat's engine, so they go upstream back to the lake. Gyarados tries to use its moves to get out, but fails. As they pass by, Ayumi wishes them luck in their task. As they sail, Cilan notices the Qwilfish robot, who electrocutes Gyarados. Cilan realizes this Qwilfish robot attacked Gyarados, causing it to be angry. Jenny notices the man and identifies him as Amer, a Pokémon poacher. Amer promises to catch Gyarados, as his Qwilfish robot cuts the net, setting Gyarados loose. Amer pulls Gyarados with his rope and as Jenny and Cilan chase him, Ayumi sees this crisis. Pansage is healed and Brock decides to take him back to his trainer, but realizes he hasn't asked Cilan's name. Ayumi comes back, reporting Gyarados is in trouble.
Gyarados tries to free itself, so Amer has Qwilfish robot release missiles to hit Gyarados' tail to calm it down. However, Gyarados focuses and uses Flamethrower, freeing itself. Amer has Qwilfish robot electrocute Gyarados, who goes to the bottom of the river. However, Gyarados uses Hyper Beam, crushing the robot and uses Outrage. Amer barely escapes, his boat being destroyed by Outrage. Cilan sends Crustle, who pins Amer to the ground. Gyarados is still attacking, so Officer Jenny and Cilan meet up with Nurse Joy and Brock at a bridge. Cilan reunites with Pansage. They see Gyarados is too furious to be reasoned, but Cilan stands up, trying to stop Gyarados. He tells Gyarados may hurt others if it goes on this rampage. Cilan admits he likes Gyarados and does not want to ruin this impression by going on this path of destruction. A log touches Gyarados' tail, who launches Hyper Beam in the sky. They all see Gyarados' tail is wounded. To calm Gyarados, Pansage takes a bit of his leaves and sings out Grass Whistle.
Brock jumps and sprays a potion on the tail, healing Gyarados. Later, Gyarados returns to its lake. Brock is fascinated by Cilan, seeing he has great courage to face Gyarados like that, almost like the friends Brock has traveled with. Cilan thinks his friend has passed the courage onto him. Next day, Officer Jenny thanks Cilan and Brock for arresting Amer. Brock replies he'd "like to get arrested", but gets hit and pulled by Croagunk. Cilan thinks Brock is a "Lady Connoisseur". At any rate, Cilan and Brock bid farewell. However, after leaving, Cilan realizes he did not ask for Brock's name.