As a Caterpie, dreaming about evolving into a Butterfree
Butterfree first appeared as a Caterpie at the end of Pokémon Emergency, where he was staring at the group as they passed by. Misty was freaked out because he was a Bug-typePokémon, and insisted that Ash do something. Ash pulled out a Poké Ball and threw it at Caterpie, hoping to catch him. In the next episode, Ash managed to successfully catch the Worm Pokémon, making him the first wild Pokémon he ever caught. Remarkably, Ash caught him without initiating a Pokémon battle, which Misty attributed to Caterpie's weakness. Caterpie was quite fond of Misty, but, much to Caterpie's dismay, she kept her distance due to fear. At night, Caterpie and Ash's Pikachu talked things over, and Caterpie revealed his desire to evolve into a Butterfree. He became very sad as he was not sure he could do it, but Pikachu offered his support.
The next day, Caterpie was the first Pokémon Ash sent out against the next Pokémon he tried to capture, Pidgeotto. With a large disadvantage against the Flying-type Pokémon, he was beaten severely and was quickly substituted for Pikachu. Later, when Team Rocket appeared to attempt to steal Pikachu, Ash sent out his weakened Caterpie after Pikachu had been blinded and Pidgeotto was defeated. Despite Team Rocket's ridicule, he managed to take down both James's Koffing and Jessie's Ekans by using String Shot and Tackle, causing Team Rocket to run away. Just as Misty was about to get over her fear and congratulate Caterpie on his victory, he suddenly evolved into Metapod, which bothered her even more.
Butterfree and Ash
In Challenge of the Samurai, Metapod was sent out in a battle against Samurai. Despite only being able to use Harden, he managed to defeat his Pinsir by solidifying so much that the Stag Beetle Pokémon's pincers broke. Samurai decided to send his own Metapod out against Ash's. Neither, however, could attack as both sides could only use the move Harden. The battle was interrupted by a swarm of Beedrill, and Metapod was carried off after Ash forgot to recall him. Ash felt guilty about this and became determined to get his Metapod back, finding it with a hive of Kakuna. Team Rocket showed up and woke up the whole hive of Beedrill with their motto, giving Ash a chance to rescue his Metapod. Despite this, the Cocoon Pokémon was unhappy with Ash, but the Trainer tried to make an excuse and claim he didn't abandon Metapod. When Ash tripped on a rock and dropped Metapod, he owned up to his mistake and swore to never leave his Pokémon behind again. Metapod was moved by this and, seeing a Beedrill about to attack Ash, leaped up and took the blow, breaking the Beedrill's stinger and getting a large gash in his shell. Metapod evolved into Butterfree and stopped all the Beedrill with his newly learned Sleep Powder attack.
In The Water Flowers of Cerulean City, Butterfree was used in Ash's Cerulean Gym battle against Misty, where he faced her Staryu. Butterfree managed to hit Staryu with Tackle and then dodged Staryu's. As Staryu landed, it lost its balance, giving Butterfree the chance to hit it with two more Tackles. Staryu scored a hit with Water Gun and kept firing off the attack. Butterfree, however, dodged them all and crippled Staryu with Stun Spore. Misty had Staryu jump into the water to wash the spores off. When Butterfree went for Sleep Powder, Staryu dodged it by diving into the water and kept using Tackle from underwater. Butterfree was struck by a Tackle and knocked into the water. With his wings wet, Ash was forced to concede the round and recall Butterfree to the safety of his Poké Ball.
In Battle Aboard the St. Anne, Ash used him in a battle against a Gentleman and his Raticate. Butterfree countered Raticate's Jump Kick with Tackle. After dodging a Hyper Fang, Butterfree crippled it with Stun Spore. As Ash was about to finish the battle, the Gentleman called the battle off and declared it a draw, despite Butterfree's almost certain victory. The Gentleman approached Ash and asked to trade the Pokémon. Ash accepted but quickly regretted the decision after realizing his attachment to Butterfree. Later, Ash managed to exchange the Raticate for his Butterfree. While he was reunited with his friend, the decision led Ash and his friends to be left trapped aboard the sinking St. Anne.
The last time Butterfree was seen with Ash was in Bye Bye Butterfree. At the start of this episode, Ash saw a large number of Butterfree flying around in the sky, and Brock told him that it was the Butterfree mating season. Ash realized that his Butterfree would probably want to have babies like the other Butterfree, so he and his friends rented a hot air balloon and watched Butterfree mingle with the others. Despite Brock's encouragement for Butterfree to choose one belonging to a cute female Trainer, Butterfree had his heart set on a pink Butterfree. He tried to impress the pink Butterfree with some fancy flying, only to be rejected with a slap to the face. Heartbroken, he flew into the woods below, followed by Ash and his friends who tried to encourage Butterfree, telling him to be assertive and tying a yellow ribbon around his neck to help him catch the pink Butterfree's eye.
Ash bidding farewell to Butterfree
Butterfree tried a second time to impress the pink Butterfree with his Whirlwind and Tackle attacks, but this tactic also failed. Then, Team Rocket showed up in a helicopter and captured all the Butterfree, with exception of Ash's, in a giant net. Butterfree pursued them, followed by the group in their hot air balloon, and they headed into a canyon where the Butterfree were stashed. While Ash handled the Rocket trio, Butterfree freed the captured Butterfree from their cage. Team Rocket tried a second time to capture all the Butterfree, only to be stopped by both Butterfree and Pikachu. Afterward, the pink Butterfree approached Ash's Butterfree and the two paired up. The two departed as Ash watched in tears, remembering what the two had been through together and wishing his dear friend a fond farewell.
As a Caterpie, he had a positive but shy attitude, shown to suffer from low self-esteem if he didn't make a good first impression. This was first shown in Ash Catches a Pokémon, where he was very hurt when Misty didn't take to him. He was also very brave, squaring up against a Pidgeotto and then both of Team Rocket's Pokémon single-handedly. His personality mellowed as a Metapod, becoming very laidback, but remained extremely loyal to his Trainer, jumping in front of a Beedrill to save him. After evolving into a Butterfree, he retained his bravery and positive attitude, but as was seen in Bye Bye Butterfree, his self-esteem still suffered when he didn't make a good first impression.
Butterfree appeared in I Choose You!, which is set in a different continuity from the main series. Like the main series, it was the first Pokémon Ash caught on his journey while it was still a Caterpie.
While exploring Viridian Forest early on in his journey, Ash encountered a Caterpie. He battled him with his Pikachu and managed to catch him. Caterpie accompanied Ash and Pikachu on their journey and became a trusted partner. While Ash was trying to catch a Pinsir by battling it with Caterpie, Caterpie evolved into Metapod.
Metapod would eventually fully evolve into Butterfree while battling a bunch of angry Primeape and subduing them with String Shot. After evolving into Butterfree, he put the Primeape to sleep with Sleep Powder. A short while after that, Ash and Butterfree encountered a pink Butterfree. Ash's Butterfree defended the pink Butterfree from a Fearow. The two Butterfree bonded but would later part ways. Not long after, the Butterfree reunited when Ash came across a herd of Butterfree, which included the pink Butterfree. Seeing how happy the two Butterfree were together, Ash decided to let his Butterfree go and said a tearful goodbye as he departed.
A † shows that the move was used recently, unless all moves fit this case or there are fewer than five known moves.
In the manga
Butterfree in The Electric Tale of Pikachu
The Electric Tale of Pikachu
Ash's Butterfree appears in The Electric Tale of Pikachu. Like in the anime, he is one of Ash's first Pokémon, however, he is the second wild Pokémon that Ash captures in the manga, the first is Fearow.
Ash's Butterfree first appears as a Caterpie and evolves into Metapod at the beginning of Play Misty For Me when Ash is showing off all of his Pokémon to Misty. Later in the same chapter, during Ash's Gym battle against Misty, Metapod evolves into Butterfree.
Ash's Caterpie was given the nickname "Felix" (Japanese: ランドルフRandolph) in Play Misty For Me, however, like the other nicknames that appear in that chapter, it seems to have been a one-off gag nickname.
Ash's Butterfree appeared in I Choose You!. It was first seen as a Caterpie. After Ash and Pikachu escaped from a flock of Spearow and their leader, Ash encountered a Caterpie and caught it.
Later, it was shown battling a Pinsir and during the battle, it evolved into a Metapod. Unfortunately, while Ash celebrated the evolution of Caterpie into Metapod, Pinsir ran away.
Metapod was sent out to deal with a bunch of angry Primeape. Ash had Metapod use String Shot on them to tie them up. This resulted in Metapod evolving into Butterfree. The String Shot didn't hold Primeape for long as they broke free from it. When the Primeape were chasing Ash and his friends, Ash had Butterfree use Sleep Powder on the Primeape, putting them to sleep. This gave the group a chance to escape before the Primeape had a chance to wake up.
Ash's Butterfree and the Pink Butterfree
Sometime after that, Butterfree was sent out to defend a Pink Butterfree from a wildFearow attacking her. Ash's Butterfree was able to drive off Fearow with Gust. Since then, it took a liking to the Pink Butterfree. While Ash and his friends were about to go to Mount Tensei, they saw a flock of Butterfree and the Pink Butterfree from before was seen. Ash sent out his Butterfree to interact with the flock. It did a courtship dance with the Pink Butterfree and she accepted. As such, Ash had no choice but to say goodbye to his Butterfree since they were migrating to the south. After some memories, Ash said a tearful goodbye to his Butterfree seeing as to how it was happy being with the Pink Butterfree.
Caterpie is the first of a main character's Pokémon who had its design changed to match new official game art, despite being introduced before the change. In a flashback in The Thief That Keeps on Thieving!, Caterpie's mouth was green as per the official Generation III game art. However, when it was first introduced, Caterpie's mouth was yellow as per the official Generation I game art.
Butterfree is the first recurring Pokémon to be caught by a main character, and the first to be released.
Butterfree was Ash's fastest evolving Pokémon, reaching his final evolution two episodes after his debut.
It is also Ash's only Pokémon to evolve in the same episode it was caught (not counting Primeape or Dragonite, who evolved prior to their respective captures).
When Metapod evolved into Butterfree, it became Ash's first Pokémon to share a type with another Pokémon already in his team; sharing its Flying type with Pidgeotto.
Butterfree has used the most status moves out of all of Ash's Pokémon, with a total of five.
Furthermore, out of all of Ash's Pokémon, excluding temporary ones, Butterfree has the least amount of damage-dealing moves, with just one.