Ash's Heracross was the first Pokémon that Ash Ketchum captured in the Johto region.
Heracross first appeared in A Sappy Ending. In this episode, a group of wild Heracross were having an argument about territory with a group of wild Pinsir. This Heracross decided to follow Ash and the gang while they worked to solve the dispute. After a battle with Team Rocket, the Pinsir and Heracross settled their differences. However, Heracross followed Ash outside of the forest, where it was happily captured by Ash.
Heracross is a strong battler, as seen in Roll on, Pokémon, where it battled against a Donphan and also in Wired For Battle, where it battled against a Scizor. Heracross has a great liking for sap, which it sucks from plants or trees. It also sucks sap from Bulbasaur's bulb, causing Bulbsaur to use Vine Whip to smack it away.
Heracross was sent to Professor Oak's lab in Tricks of the Trade so Ash could add one of his Tauros to his party. Although Tauros was returned to Prof. Oak in the next episode, the professor asked Ash to leave Heracross with him for a while, as he wanted to study its behaviour.
Heracross was used in Ash's Johto League battle against Gary in The Ties that Bind. It managed to defeat Gary's Magmar, however in the following episode, Heracross was defeated by a Hydro Pump from Gary's Blastoise.
Ash used Heracross in his battle against the Palace Maven Spenser in Ka Boom With a View! Immediately after being released from its ball, Heracross went to start sucking the sap from Spenser's Venusaur's flower. Heracross was defeated by Venusaur's SolarBeam after a hard-fought battle.
Heracross appeared again in An Old Family Blend, where it was shown to be sucking the sap from Bulbasaur at Prof. Oak's lab and also sucking Oak's head. In the following episode, Ash used Heracross to battle Nando and his Kricketune. Kricketune used Sing to put Heracross to sleep, but Heracross managed to dodge Kricketune's Fury Cutter with Sleep Talk and counter it with Focus Punch. Heracross soon woke up and battled fiercely with Kricketune and managed to defeat it with a combination of Megahorn and Horn Attack. Heracross then began sucking on Ash's head.
Heracross was the first Pokémon used by Ash to battle Tobias' Darkrai in The Semi-Final Frontier. Heracross was revealed to know Hyper Beam, which clashed with Darkria's Ice Beam. Darkrai's Dark Void put Heracross to sleep, but thanks to Sleep Talk, Heracross managed to hit Darkrai with Megahorn, causing serious damage. However Heracross was defeated when Darkrai attacked it with Dream Eater and Darkrai restored its energy at the same time.
|Tackle||Roll on, Pokémon|
|Horn Attack +||Roll on, Pokémon|
|Endure||Roll on, Pokémon|
|Leer||Wired For Battle|
|Take Down||Wired For Battle|
|Fury Attack||Wired For Battle|
|Megahorn +||The Ties that Bind|
|Sleep Talk +||League Unleashed!|
|Focus Punch||League Unleashed!|
|Hyper Beam +||The Semi-Final Frontier!|
|+ indicates this Pokémon used this move recently.*|
- indicates this Pokémon normally can't use this move.