Dueling Heroes (Japanese: うずまきカップ！みずのコロシアムでだいバトル！！Whirlpool Cup! A Big Battle in the Water Colosseum!!), is the 216th episode of the Pokémon anime. It was first broadcast in Japan on September 20, 2001 and in the United States on October 26, 2002.
As the final round of the Whirl Cup begins, Ash and Misty must each face formidable opponents. Ash has his Kingler transferred from Oak's lab in preparation, but when he and his Totodile begin their first battle, they must face an opponent with a powerful Kingdra. Misty also faces a challenging duel with an experienced opponent and his Qwilfish. Meanwhile, Team Rocket sets about stealing an ancient jewel used in a reward ceremony to be performed for the tournament's victor.
The day begins with everyone waiting for the Whirl Cup Colosseum as the water drains out somewhat. Soon all the Trainers and audience watch Maya. She congratulates them as well as wishing them a little luck. She then puts her staff that has a sapphire at the end towards the sun which makes the area glow bluish for a while. The prize given to the winning Trainer is a pendant that helps the WaterPokémon who wears it. Team Rocket, acting as vendors, gazes upon the staff more than the pendant. They formulate a scheme to try to snatch it.
The way the Whirl Cup tournament goes is a two "block" division; Ash and Misty are in block "A". Ash notices he only has one Water Pokémon, so he calls Professor Oak to swap a Pokémon for Kingler. He puts in Bayleef and he gets Kingler. Back at Professor Oak's Laboratory, Oak releases Bayleef, but Bayleef gets very sad from being away from Ash and runs around eventually ramming into Oak. The first day all contestants in block A fight off. Ash and Misty sort of get into a fight before the first match begins but Brock helps settle things out.
The second round of Block A pits Ash against Christopher. Ash uses Totodile for this round and his opponent calls out Kingdra. Ash takes a quick scan on it and Brock in the bleachers comments to Misty that Ash might not have a good time with this one. Being Water/Dragon, Totodile's Water attacks are practically useless. Ash takes the lead and commands Totodile to dive under the water but Kingdra counters with a Twister. Totodile snaps out of it and lands on one of the platforms. After that, Kingdra shoots a Hydro Pump at Totodile, but Totodile simply walks along the water and gets close enough to do a Headbutt, but Kingdra dives, Totodile doing the same. Kingdra releases a Smokescreen that covers up the water. With no other option, Ash tells Totodile to jump out of the water. The battle comes to a standstill because it was expected that Ash would have Totodile risk it and jump back in. Fed up, the Trainer tells Kingdra to jump up and try another Hydro Pump. Ash however tells Totodile to use Bite on Kingdra, aiming for the snout. Totodile is successful and plugs up Kingdra's snout causing all the water to hold back. After a while Totodile releases and Kingdra goes flying across and eventually getting knocked out. Ash wins the match. After the match, Team Rocket is still devising a plan to get Maya's staff. Except a supervisor comes by and they seem to have a strong patriotism to the sales pitch. Later that night Misty stares at the coliseum from the Pokémon Center window thinking. Ash notices and they have the talk about what will happen if they end up battling each other.
The third round of Block A has Misty battling Harrison. Harrison is one of the older Trainers, so he has a snobbish attitude when he steps up to the arena. The match is on, Corsola against Qwilfish. Qwilfish begins the match by shooting a Water Gun but Corsola reflects it back with a Mirror Coat. Seeing that this tactic won't work Harrison tells it to start swallowing water. As the announcer says that this is used for preparing a volley of spikes, Misty thinks fast. Qwilfish soon releases Pin Missile and so Corsola counters with Spike Cannon. The two attacks explode in mid air knocking Corsola back but Qwilfish took refuge in the waters. Taking advantage of this Qwilfish makes a Take Down attack to Corsola. Worried that Corsola is going to burn out anytime, Misty tells it to use Recover, however Qwilfish has already started up another Take Down. By the time Corsola recovered, Qwilfish already zeroed in. Corsola and Qwilfish dive down and Qwilfish reappears, but so does Corsola, below Qwilfish. Qwilfish is stuck on Corsola's head and can't do much about this so it just swims around. Misty finally gets an idea and tells Corsola to use Spike Cannon. Corsola fires the Spike Cannon sending Qwilfish sky-high, Misty winning the match. During the battle, Team Rocket make their move towards Maya's staff but they failed. Officer Jenny is there and notices them, so they quickly get out their snacks-for-sale and pretend they were going to sell them.
Back at the Pokémon Center, Ash and Misty wait for the results of the tournament, and it turns out that Ash is up against Misty for the next round.