Green obtained Charizard when it was a Charmander in Professor Oak's laboratory. He chose Charmander to make Red's life easier as Red had trouble deciding which one of the three he wanted. Green tests Charmander's strength over a Clefairy that barged in the professor's lab. Charmander does so by burning Clefairy's tail, which makes the Normal-type run in panic, setting the lab ablaze. Around that time, Green and Charmander already left. Later in Big Battle in the Viridian Forest!!, Charmander carries a bag of Poké Balls during Green's visit with Red to show him the amount of Pokémon caught. During Clefairy's treatment at the Pokémon Center, Green has Charmander throw a fly in the window to sabotage the process.
Charmander challenges its first Gym battle in Bring Down the Powerful Opponent Onix!! against Brock's Onix where it was easily taken out by the rock snake. During the search for a Mew that took the Moon Stone Red wanted which took place in Search For The Mirage Pokémon Mew!!, Charmander leads Red and the others to an abandoned water mill. Charmander battles Clefairy after Green tries to capture the Mew that Bill's wife transformed into. Clefairy changes into a firefighter which made Charmander laugh. Charmander then evolves directly into Charizard, skipping the Charmeleon stage. Charizard was getting difficult for Clefairy to beat. However, Bill uses one of his machines to shrink Charizard only for Clefairy to get in the shrinking process too. Charizard later devolved to its basic stage way after it along with Green ran away from Bill's house after seeing his hideous appearance.
In Pikachu Was Kidnapped!!, Charmander was seen along with Green in the Game Corner playing the slots, rivaling Red and his two pals. In Big Struggle with the Powerful Opponent Venusaur!!, Charmander destroyed Red's boat by using Flamethrower on it so that Green would be way ahead of Red.
Charmander evolved into Charizard again in The Legendary Pokémon Appears!! during the search for Articuno in the Seafoam Islands cave. After getting into the end of the cave, it devolved back into Charmander. They managed to find Articuno only for both Charmander and Green to get frozen by the Legendary Bird's Blizzard despite Charmander having the type advantage.
Charmander had already evolved in Get the Flying Machine!! where it was seen carrying Green on its back. Next to them was Blue, Doduo and his Blastoise after they beated Red in getting the flying machine. It returned to its base form in Aim to be the No. 1 Pokémon!, only for it to do the process again in the next chapter to pull a heavy Snorlax. Charmander evolved into Charizard before The Final Battle!!. It is unknown if it stayed as a Charizard permanently or reverted back to Charmander since then.