Caterpie first appeared at the end of Pokémon Emergency, staring at the group as they passed by. When Misty freaked out about its type and told Ash to do something, Ash pulled out a Poké Ball and threw it at Caterpie, hoping to catch it. In the next episode, Ash managed to catch the Worm Pokémon, being the first wild Pokémon he ever caught. Ash remarkably caught him without a Pokémon battle, which Misty attributed to Caterpie's weakness. Caterpie was quite fond of Misty, but, much to Caterpie's misfortune, she wanted nothing to do with him because it was a Bug-type Pokémon, which she feared. At night, Caterpie and Ash's Pikachu talked to each other, and Caterpie revealed its desire to evolve into a Butterfree. It became very sad as if it was not sure it could do it, but Pikachu encouraged it.
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, it was beaten severely and was quickly substituted for Pikachu. Later, when Jessie, James, and Meowth appeared to attempt to steal Pikachu, Ash sent out his weakened Caterpie against them after they had blinded Pikachu and defeated Pidgeotto. Despite being made fun of by Team Rocket, it 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 its victory, it suddenly evolved into Metapod, which bothered her even more.
In Challenge of the Samurai, Metapod was sent out in a battle against Samurai. Despite only being able to use Harden, it managed to defeat his Pinsir by solidifying so much that the Stag Beetle Pokémon's pincers broke. Samurai then decided to send his own Metapod out against Ash's. Neither, however, could attack, and both had to sit stationary and keep hardening. The battle was then interrupted by a swarm of Beedrill that snatched Ash's Metapod away when he forgot to pick it up before running off. 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. Metapod, however, 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 its shell. Metapod then evolved into Butterfree and stopped all the Beedrill with its Sleep Powder attack.
In The Water Flowers of Cerulean City, Butterfree was used in Ash's Cerulean Gym battle against Misty, where it 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 then 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 jumping into the water and kept using Tackle from underwater. Butterfree was then hit by another Tackle, knocking it into the water. As Butterfree was unable to swim, Ash was forced to concede the round and recall Butterfree to the safety of its Poké Ball.
Butterfree battled A.J.'s powerful Sandshrew in The Path to the Pokémon League. Butterfree went for Stun Spore, but Sandshrew avoided it using Dig and then knocked Butterfree out.
Butterfree being traded for Raticate
In Battle Aboard the St. Anne, Ash used it in a battle against a Gentleman with a Raticate. He 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 then approached Ash and asked to trade the Pokémon. Ash accepted but soon found that Butterfree meant too much to him to keep the Raticate, and was so set on trading them back that he did it while the St. Anne was sinking, causing him and his friends to be trapped inside.
In Tentacool & Tentacruel, Butterfree bore Bulbasaur into battle with a giant Tentacruel, but was knocked out by Tentacruel's attack.
Ash's Butterfree with its mate
Ash bidding farewell to Butterfree
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 found its heart set on a pink Butterfree. It tried to impress the pink Butterfree with some fancy flying, only to be rejected with a slap in the face. Heartbroken, it flew into the woods below, followed by Ash and his friends who tried to encourage Butterfree, telling it to be assertive and tying a yellow ribbon around his neck to help him catch the pink Butterfree's eye. Butterfree tried a second time to impress the pink Butterfree with its Whirlwind and Tackle attacks, but this failed as well. Then, Team Rocket showed up in a helicopter and captured all the Butterfree but Ash's in a giant net. Butterfree pursued them, followed by Ash and friends in their hot air balloon, and they headed into a canyon where the Butterfree were stashed. They broke in and Ash battled Team Rocket while Butterfree used its Tackle against the cage the Butterfree were in, finally getting the attention of the pink Butterfree. It broke open the cage, and the Butterfree all flew free. Team Rocket tried a second time to capture all the Butterfree, only to be stopped by both Butterfree and Pikachu. Afterwards, 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.
Ash's Butterfree has since appeared in the tenth opening for the anime, Spurt!, along with its mate, the pink Butterfree. However, it has not returned in any episodes since its last appearance. Ash has, however, flashed back to having it several times, such as in The Thief That Keeps on Thieving!, A Trainer and Child Reunion!, Butterfree and Me!, and Alola, Kanto!.
Butterfree reappeared in I Choose You!, which is set in a timeline different from the main anime. As such, it first appeared as a Caterpie that was captured by Ash. Caterpie's evolution into Metapod occurred whilst battling a Pinsir instead of Team Rocket, whilst Metapod evolved into Butterfree during a battle against a pack of Primeape instead of a swarm of Beedrill.
Its storyline in the film is otherwise similar to the storyline in the original series. Butterfree was ultimately released to take part in a mating migration with the Pink Butterfree.
Butterfree in The Electric Tale of Pikachu
In The Electric Tale of Pikachu manga
Ash's Butterfree appears in the manga series 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 and is captured as a Caterpie in Pikachu, I See You!. He 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 Butterfree is seen again in Clefairy Tale battling a wild Onix and in Haunting My Dreams battling the Black Fog, but he is not used again after that. He may have been released like he was in the anime, however, no scenes implying this are shown in the manga. Butterfree is not shown when Ash brings his entire party out of their Poké Balls in You Gotta Have Friends.
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.
| Using Harden as a Metapod
| A † shows that the move was used recently, unless all moves fit this case or there are fewer than five known moves.