It starts off with Red and Blue, his rival, going to Professor Oak's lab to receive a PokéDex, PokéBalls, and their first starter Pokémon. Blue lets Red choose first. Red chooses a Charmander because it is a Fire-type like he is named after. Blue chooses Squirtle. Oak asks them to fill the Pokédex with the 149 known Pokémon and they excitingly accept the task. Red sees a Pidgey but fails to capture it and finds out that in order to fill the Pokédex he must capture all 149 Pokemon. He then sees and captures his first Pokémon, Rattata. Soon he captures Spearow, Caterpie, and Pidgey. While fighting a trainer, who has a Nidoran♀, he attempts to capture that as well but finds out that he can only capture wild Pokemon and the trainer tells him where he caught that Pokémon. While walking towards that area he finds Blue again and they battle 1 on 1. Blue wins the battle. Afterwards, Red's confronted by Brock, who tells him that Pokemon and their trainers need to grow stronger together and tells him to begin challenge the Gym Leaders.
Red heals his Pokémon and heads to Pewter City to challenge the Gym Leader, who turns out to be Brock. Brock only uses two of his Pokémon, Geodude and Onix, while Red uses five of his Pokemon: Charmander, Spearow, Rattata, Metapod, and Nidoran♂. Red ends up winning and receives his first Gym badge. Red buys a "rare" Magikarp from a salesman for $500. He then goes through Mt. Moon and gets the Helix Fossil and also beats the Team Rocket members there and another at Cerulean City. He was able to take down Misty and Lt. Surge to win his second and third badges. Sometime during this, his Charmander evolved into Charmeleon. He received the TM Dig, the HM Cut, a bike, and an Old Rod during his travels. He had captured 42 Pokemon at this time.
After traveling through the Rock Tunnel, Red arrives at Lavender Town. While he was healing his Pokémon at the Pokémon Center, he overhears stories about ghosts in Pokémon Tower. Before heading there, he stops by the Pokémon House as the Nurse requested. He sees many abandoned Pokemon, including a Cubone whose mother was killed by Team Rocket and was rescued by Mr. Fuji, the owner of the Pokémon house. Red finds out Mr. Fuji had gone missing after going to Pokemon Tower and decides to go looking for him. Blue overhears this and decides to go too. Red takes on the ghost with Charmeleon but cannot defeat it until Blue comes and gives him the Silph Scope, which reveals the ghost to be Cubone's mother. Cubone then comes and hugs its mother who disappears after, seeing that her son is alright. Red then uses Jolteon to defeat Team Rocket and save Mr. Fuji, who gives Red a Pokéflute and a box of unknown gems. Red then sets out for the next town on his adventure.
Red and Charmeleon defeat Erika's Vileplume and win the Rainbow Badge. He finds a secret Team Rocket base in the same city and infiltrates it. He battles Team Rocket, releases all the Pokémon there and meets the leader of Team Rocket, Giovanni. He later finds, wakes up, battles and captures a sleeping Snorlax. He receives the Good Rod from the brother of the guy that gave him the Old Rod and uses it to capture a Psyduck. Red defeats the ninja Gym Leader Koga and gets the 5th Gym Badge. After countless battles, his Charmeleon evolves into Charizard. Red had captured 65 Pokémon at this time. Red and Blue find a woman and help her escape from Team Rocket. She tells them about the Master Ball project and that Team Rocket's using Pokémon as test subjects to experiment on. Red orders Blue to tell the police while he storms Silph Co. and frees the Pokémon. He meets Giovanni again, who battles Red's Charizard with his Nidoqueen and wins before escaping with the rest of Team Rocket.
The Ultimate Gym Leader
After Saffron City, Red challenges Sabrina and defeats her Alakazam with Haunter. A scientist he frees thanks him and gives him his Lapras. He beats the Karate Master and wins his Hitmonlee. He and Lapras travel to Cinnabar Island where Red goes to the Pokémon mansion and reads about Mew and Mewtwo. He then battles and defeats Blaine. After hearing that the Viridian City Gym Leader - the strongest of them all - has returned, Red decides to challenge him. He arrives just as Blue walks away, having already beaten the Gym Leader. Red challenges the leader who turns out to be Giovanni. Red is shocked that Team Rocket owns a Gym. Comparing Giovanni to the other Gym Leaders he battled, Red angrily points out that unlike Giovanni, the other Gym Leaders actually loved their Pokemon Giovanni disregards his rebuke. Red declares that he no longer wants a Gym battle, but to fight him for all the things he did to Pokemon worldwide. Giovanni then grabs two Ultra Balls and accepts the battle. He uses Rhyhorn and defeats Red's Victreebel, Kabutops, Snorlax and Jolteon. Red's Hitmonlee manages to take Rhyhorn down, fainting in the process. With both of them down to their last Pokemon, Giovanni uses Rhydon and Red calls out Charizard, who's able to defeat Rhydon despite the type disadvantage. Giovanni offers Red the badge, but he refuses to take anything from the Rocket leader. Reminded of the Trainer he used to be from observing Red during their battle, Giovanni disbands Team Rocket so that the badge would be from the Viridian City Gym Leader rather than the gang's boss. Accepting this, Red takes the badge.
The Pokemon League
After making it through Victory Road, Red battles and defeats the Elite Four, using Jolteon, Scyther, Dodrio, Lapras, Persian and Charizard. Lance was about to announce him Champion, but revealed there was one more Trainer he had to fight: Blue, who'd defeated Lance and became the Champion. Blue sends out Pidgeot first while Red uses Jolteon. Jolteon defeats Pidgeot. Red's Scyther battles Blue's Alakazam and they both faint. Blue's Rhyhorn is defeated by Red's Lapras, who's defeated by Arcanine. Red's Dodrio gets defeated by Blue's Exeggutor, but later is defeated by Persian. Jolteon's defeated by Blastoise and Red is down to one Pokemon left: Charizard, who he sends out for the last round. Charizard and Blastoise battle it out until the end in which Charizard wins. Oak then appears, naming Red the Champion and putting him and his Pokemon in the Hall of Fame.
Red continues to complete the Pokédex, capturing the Legendary Birds Zapdos, Articuno and Moltres. Once he captures all 149 Pokemon, Red finds out Blue was majorly injured by an unknown Pokemon and sets out to capture it in Cerulean Cave. The Pokemon is Mewtwo who proves to be especially powerful, defeating all of Red's Pokemon one by one, including the Legendary Bird Articuno, leaving Red with only Charizard remaining. Charizard and Mewtwo go at it and Mewtwo knocks both Pokemon and Trainer into the waters nearby. As he and Charizard sink towards the bottom, Red notices that Charizard hasn't given up yet. As he and Charizard float towards each other, the Mega Stones given to him by Mr. Fuji start to glow in Red's pocket. Red takes the Mega Stones out and sees Charizard glow with them. The two appear to converge in the water, causing a huge blast.
Out of the water emerges Charizard, having Mega Evolved into a new form, Mega Charizard X, via the power of the Mega Stones. Red then pits Mega Charizard X against Mewtwo, the former now powerful enough to match the latter. After a quick yet intense battle, Red has Mega Charizard X finish Mewtwo off with a final Megaton Punch, slamming Mewtwo into a nearby stalagmite. Taking the chance, Red throws an Ultra Ball at Mewtwo. The Ball slows and stops, emitting stars, indicating a successful capture. Red happily embraces Charizard for a job well done.
Having now captured all 150 Pokemon, Red returns to Professor Oak's laboratory where he eats cake with Oak, the assistant and Green, who expresses jealousy that he wasn't the one to capture Mewtwo. Red then remembers reading that Mewtwo was the child of another Pokemon, Mew, and arrives at the conclusion that there's a 151st Pokemon in existence. Standing up from the table, Red announces he has to find Mew, presumably to capture it and add it to the Pokedex.
Being Red's first Pokemon, it is his strongest. As a Charmander, he defeated Onix and Starmie despite the type disadvantage. Charmander later evolved into Charmeleon and eventually Charizard. Charizard was eventually defeated by Giovanni with his Nidoqueen. The defeat made Red train his Pokemon harder. Charizard eventually defeated Giovanni's Rhydon, proving stronger than before. Charizard even defeated Blue's Blastoise, Moltres, and Mewtwo.
After failing to capture a Pidgey, Red battled and captured Rattata, his first Pokemon he captured. Rattata's speed came in handy when he battled Onix, although it was easily defeated. It is unknown what has become of Rattata but it may be possible that it evolved into Raticate, although this is unconfirmed.
Spearow was Red's second Pokemon captured. Spearow's flying speed came in handy when battling Brock, but it was also easily defeated. It is unknown what has become of Spearow but it is likely that it never evolved due to Red trying to catch a Fearow later on.
After catching Spearow, Red went to capture Caterpie. Although unconfirmed, it is likely that Caterpie evolved into Metapod because wild Metapod only know Harden while Red's Metapod used Tackle and String shot. It is unknown what has become of Metapod but it is likely that it evolved into Butterfree, although this is unconfirmed.
Despite failing to capture his first Pidgey, Red later encountered another and captured it. Although it was never used against Brock, it is likely that it evolved into Pidgeotto and later Pidgeot, although this is unconfirmed.
It is presumed after the trainer showed where to catch his Nidoran, Red captured this one, although it was the male version. Nidoran♂ assisted Red in defeating Brock's Geodude and weakening his Onix with Double Kick. It is unknown what has become of Nidoran♂, but it is possible that Red evolved it into Nidorino and later Nidoking, however this is unconfirmed.
Red bought this Magikarp for $500 because the salesman said it was rare and powerful, despite being one of the weakest Pokemon. It is, however, possible that Red evolved Magikarp into Gyarados, although this has not yet been confirmed.
While freeing the Pokemon and scientist from Team Rocket, one person gave Red a Lapras. Since then, Red has used Lapras to travel to Cinnabar Island, defeated Lance in the Pokemon league, and capture a Tentacool.
While traveling through Mt. Moon, Red encountered a scientist that refused to share his fossils. After battling him, Red received one of the fossils. While at Cinnabar Island, Red turned the fossil into a Kabuto, which later evolved into Kabutops. Kabutops was used against Giovanni's Rhyhorn, only to be defeated despite it's powerful moves, such as Hydropump and Slash.
After beating the Pokemon League, Red continued looking for Pokemon to fill his PokeDex. He encountered Tentacool while surfing with Lapras. He was able to defeat and catch it. It may be possible that he evolved Tentacool but this is unconfirmed.
After beating the Pokémon League, Red continued looking for Pokemon to fill his Pokedex. He encountered Pikachu while traveling in the Viridian forest. Red was excited to see one and quickly caught it. It is unknown if Red decided to evolve Pikachu but it is unlikely as the show is based off the game, in which Pikachu never evolved.
After beating the Pokemon League, Red continued looking for Pokemon to fill his PokeDex. He encountered Chansey while in the safari Zone. He was deciding to use either bait or Rock when the Chansey began to leave, to which Red followed and captured Chansey.
On his journey to complete the Pokedex, Red ran into the legendary bird, Articuno. Red used Rapidash to capture him in an Ultra Ball. Articuno was later used against the powerful Mewtwo. However, even a legendary Pokemon could not defeat him.
After Blue came home from being broken, Red and Oak used his completed Pokedex to try to identify it. When none of the 149 Pokemon looked like it, they deemed it as a new species of Pokemon. Red remembered a book, Dr. Fuji's diary, about them creating a new Pokemon, the son of Mew, Mewtwo. Red then took his strongest Pokemon there (Gengar, Lapras, Articuno, Charizard, and two others, most likely Zapdos and Moltres) to Cerulean Cave. Despite type advantages and legendaries, no Pokemon could defeat it until Red's Charizard mega evolved and took down Mewtwo. Mewtwo was then captured with an Ultra Ball.