Diamond & Pearl series
As a Chimchar
, while under Paul's command
Infernape was once a Chimchar owned by Paul. Prior to events of the Diamond and Pearl series, Paul saw Chimchar being chased by a group of wild Zangoose. The situation looked bad for Chimchar, but in its stress it pulled off an extremely powerful Flame Wheel. This impressed Paul enough to add Chimchar to his regular team. However, this first impression did not match up to Chimchar's normal abilities, resulting in Paul criticizing it for being weak. Traumatized, Chimchar gained a morbid fear of all Zangoose.
Chimchar's first episode was When Pokémon Worlds Collide! where Paul used it to battle Ash's Aipom. It fought well, but lost in the end. Chimchar reappeared in Different Strokes for Different Blokes where it won against Ash's Turtwig and Shapes of Things to Come! where it beat Roark's Onix but lost to Roark's Cranidos.
After losing to Cynthia's Garchomp in Top-Down Training, Paul realized that Chimchar was not fulfilling his expectations. This culminated in the Hearthome City Tag Battle Competition, where he was forced to battle alongside Ash. That night, Ash discovered Paul's training regime, which involved his Pokémon attacking Chimchar in the hopes of recreating the power he had seen before. Ash intervened and took Chimchar to the Pokémon Center where Nurse Joy told Paul it would be unable to battle. Paul ignored this warning.
During the next battle against a Zangoose and a Metagross, Chimchar was too scared to make any attack when caught in Zangoose's claws, and had to be saved by Turtwig, who was seriously injured as a result. Chimchar made up for this by protecting Turtwig from a Fire Blast attack. Furious at Chimchar, Paul refused to give any orders. Consequently, Ash gave Chimchar commands for the remainder of the battle. After the battle, Paul released Chimchar in front of Ash. As the little Pokémon headed back to the wild, Ash invited it to join him, to which it accepted. Paul rudely commented that the two were perfect for each other: both were worthless scum.
Ash offering Chimchar to join his party
Immediately after being released and offered to join Ash, Chimchar was kidnapped by Team Rocket, but used Flamethrower on the mecha they had used to steal it, blasting them off. It then promptly joined Ash.
In the final round of the competition, Paul and Ash selected Elekid and Chimchar for their last battle in Smells Like Team Spirit! against Conway's Heracross and Dawn's Buizel. During the battle, Elekid evolved into Electabuzz, and they both combined Thunder and Flamethrower on Buizel and Heracross to knock them out. This victory meant that Ash and Paul won the Hearthome City Tag Battle Tournament.
In Tears For Fears!, Ash and his friends had a picnic party. Chimchar watched as Ash, Dawn, and Brock's other Pokémon had fun playing, battling, and helping cook together. Chimchar began to have flashbacks of when it was still in Paul's possession, reflecting on how its former Trainer abused it and treated it like nothing more than a tool for battle, giving it a few minutes to eat before going back to extensive training, as opposed to how Ash and his friends treat their Pokémon like friends, caring for them and not pushing them too hard. Chimchar began to cry out of joy that it was finally treated with patience and kindness, something Paul failed to do as its Trainer. In the same episode, Chimchar was faced with the challenge of battling three Zangoose in order to save Ash's Pokémon. Though Chimchar had a morbid fear of Zangoose, with Ash's encouragement Chimchar was able to overcome this fear and save the other Pokémon, getting rid of Team Rocket in the process as they were sneaking off.
In A Triple Fighting Chance! Ash used Chimchar in his Gym Battle against the Veilstone City Gym Leader, Maylene. Chimchar battled Meditite, but was recalled after Meditite confused it. It was then sent out against Lucario where it was ultimately defeated, despite a valiant effort.
In Chim - Charred! Ash, Dawn, and Brock ran into Paul. Ash and Paul had an argument about training methods, and an enraged Ash challenged Paul to a battle. Chimchar volunteered to go up against Paul and faced Paul's Ursaring. Ursaring and Paul used brutal tactics, and Chimchar was pushed to the point of using Blaze. Chimchar easily defeated Ursaring, but went on an uncontrollable rampage. Ash grabbed a flaming Chimchar, begging it to stop. Chimchar continued to struggle and even went as far as to bite Ash in its rage. Eventually, after being embraced by Ash, Chimchar calmed down.
Later in Double Team Turnover!, when battling Team Galactic, Chimchar protected Pikachu from a Poison Jab launched by Saturn's Toxicroak. Chimchar was incapacitated for the rest of the fight, and was later thanked by Ash (after receiving medical treatment). Cynthia then comforted Chimchar about its past with Paul.
Ash later used Chimchar to battle against Barry in Barry's Busting Out All Over!. Chimchar easily defeated Barry's Staraptor, using its superior agility. However, despite the type advantage, Chimchar lost to Barry's Roserade.
In Shield with a Twist!, using Ash's counter-shield strategy, Chimchar defeated Fantina's Mismagius and Drifblim, earning Ash his Relic Badge.
In Dealing With Defensive Types!, it was used in the battle against Byron's Bastiodon, Bronzor and Steelix. It defeated Bronzor and Steelix, but eventually fell to Bastiodon. This mirrors Staravia's previous participation in the third Gym, with it defeating the Gym Leader's first two Pokémon and losing to their third.
In Sliding Into Seventh!, it was used in the Snowpoint Gym battle. Chimchar battled Candice's Snover and Abomasnow, and despite a harsh battle with Abomasnow, it defeated both of them, earning Ash his Icicle Badge.
In Evolving Strategies!, Chimchar was used in the full battle Ash had against Paul. It defeated Paul's Ursaring, which had previously taken down three of Ash's Pokémon, and evolved soon after into a Monferno, immediately learning Mach Punch. During the following battle against Paul's Electabuzz, it put up a very close fight, but was defeated in a clash of Mach Punch and ThunderPunch, and badly injured, resulting in a loss for Ash.
In Uncrushing Defeat!, Monferno, along with the rest of Ash's Pokémon, was badly injured. It needed a Cheri Berry to help treat it, but the Pokémon Center didn't have one. After Brock got one by Lake Acuity, it became recovered slightly. It eventually attacked Team Rocket in combination with Ash's other Pokémon.
In Bagged Then Tagged!, it was used in a Tag Battle with Dawn against Lyra and Khoury. Monferno used Flamethrower on Dawn's Cyndaquil's Flame Wheel to defeat Lyra's Chikorita, and defeated Khoury's newly evolved Croconaw with a Mach Punch.
Infernape's Ability activated
In Fighting Ire with Fire!, Monferno battled Barry's Empoleon. After being struck by a Hydro Cannon and sent crashing into the forest nearby, Monferno entered once again into an uncontrollable rampage with Blaze, but managed to control it in the last second in order to save Ash's Pikachu, Dawn's Piplup, Paul's Electabuzz and Barry's Empoleon from Team Rocket's falling mecha, evolving into an Infernape in the process.
In Flint Sparks the Fire!, Ash used Infernape in a battle against Flint's Infernape. However, despite its power and speed, it was unable to keep up with Flint's Infernape and was quickly knocked out with a Mach Punch.
In The Eighth Wonder of the Sinnoh World!, Infernape participated in Ash's rematch against Volkner. It defeated Volkner's Jolteon with a Mach Punch. When it battled Volkner's Luxray, it took severe damage, pushing it to activate Blaze. This time, however, Infernape was able to control itself and defeat Luxray with a powerful Flame Wheel, giving Ash the victory and the Beacon Badge.
The principal rivalry between Infernape and Electivire
Before the Lily of the Valley Conference, Ash decided he would need help from his previously caught Pokémon. Due to this, Infernape, along with Ash's Sinnoh party (save for Pikachu) were all sent to Professor Oak's Laboratory. Later during the tournament Ash recalled Infernape to his team and trained against Brock's Sudowoodo to improve Flame Wheel when Infernape suddenly learned Flare Blitz.
Infernape was later used in the full battle against Paul's Aggron, where it managed to burn Aggron with Flare Blitz before finally defeating it with Mach Punch. Ash decided to recall it when Paul sent out his Gastrodon. Later on it was sent out again to battle Paul's Ninjask. Ninjask's Agility was getting the better of it so Ash told it to use Dig then Flare Blitz which heated up the field, causing fire to erupt out of the ground, which made a mist cover the whole field that drastically damaged Ninjask and also cancelled Drapion's Toxic Spikes attack. After putting up a good fight, Infernape was able to put an end to Ninjask's lightning speed with a Mach Punch, evening the score. Infernape's final opponent was Paul's Electivire in a heated battle in Battling a Thaw in Relations!. Infernape initially caused Electivire severe damage, but after a while, it was caught by Electivire's tail, and took so much damage from Electivire's Thunder attack that the referee had almost declared it unable to battle. But, Blaze was once again activated, giving Infernape the strength to defeat the Thunderbolt Pokémon with a devastating Flare Blitz attack, giving Ash his first victory against Paul as well as access to the Semifinal Round of the Lily of the Valley Conference.
Ash left Infernape at Professor Oak's Laboratory when he decided to go to Unova.
Best Wishes series
Infernape was reunited with Ash in The Dream Continues!, where it and the rest of Ash's Pokémon posed in a group photo with him.