Caterpie first appeared at the end of Pokémon Emergency, staring at the group as they passed by. When Misty freaks out about its type and tells Ash to do something, Ash pulls out a Poké Ball and throws it at Caterpie, hoping to catch it.
In Ash Catches a Pokémon, he was the first wild Pokémon Ash ever caught. Throwing a Poké Ball at a Caterpie he encountered in Viridian Forest, 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 he was a Bug-type Pokémon, which she feared. The night after he was captured, Caterpie and Ash's Pikachu talked to each other, and Caterpie revealed his desire to evolve into a Butterfree. He then became very sad, as if he was not sure he could do it, but Pikachu encouraged him. He fell asleep next to Misty, who screamed at him the next morning for this and hurt his feelings.
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. Despite this, when Jessie, James, and Meowth appeared to attempt to steal Pikachu, Ash sent out his weakened Caterpie against them. They laughed, but Caterpie had the last laugh, taking down both James's Koffing and Jessie's Ekans by himself using String Shot and Tackle. Just as Misty was about to get over her fear and congratulate Caterpie on his victory, he 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, he 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 could attack, and both had to sit stationary and keep hardening. This was interrupted by a swarm of Beedrill that snatched Ash's Metapod away when he forgot to pick him up before running off. Ash felt guilty about this and became determined to get his Metapod back, finding him 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. He was unhappy with Ash, but the Trainer tried to make an excuse and claim he didn't abandon Metapod—however, when he tripped on a rock and dropped Metapod, Ash 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, leapt up and took the blow, breaking the Beedrill's stinger and getting a large gash in his shell. Metapod then evolved into Butterfree and stopped all the Beedrill with his Sleep Powder attack.
While he was with him, Butterfree was a close companion of Ash's who fought in many battles, although he did not have the battling pedigree of his Pikachu. Most of his battles resulted in losses, including his battle against Misty at the Cerulean Gym during The Water Flowers of Cerulean City, his only battle against a Gym Leader. Here, he managed to cripple her Staryu with Stun Spore, but Staryu recovered underwater. When Butterfree attempted a Sleep Powder, Staryu knocked Butterfree into the water with Tackle. As Butterfree was unable to swim, Ash was forced to concede the round and recall Butterfree to the safety of his Ball.
He also battled A.J.'s powerful Sandshrew in The Path to the Pokémon League, but was knocked out by Dig. Ash took morbid offense at Sandshrew's ability to defeat the Flying-type with a Ground-type move (something not normally possible). His third successive loss was in Bulbasaur and the Hidden Village, to a wild Bulbasaur. Bulbasaur blew Butterfree's Sleep Powder back at him, deterring him long enough for Bulbasaur to escape.
Butterfree being traded for Raticate
In Battle Aboard the St. Anne, Ash used him in a much more successful battle against a Gentleman with a Raticate, blocking Raticate's Jump Kick with Tackle and then crippling it with Stun Spore. However, 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 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 his 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, and 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 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 in 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. Butterfree tried a second time to impress the pink Butterfree with his 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 his Tackle against the cage the Butterfree were in, finally getting the attention of the pink Butterfree. He 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.
It is a common misconception that Butterfree die after mating. This comes from a mistranslation and there is nothing to stop Butterfree returning in the future.
Ash's Butterfree has since appeared in the tenth opening for the anime, Spurt!, along with his mate, the pink Butterfree. However, he has not returned in any episodes since his last appearance. Ash has, however, flashed back to having him several times, such as in The Thief That Keeps on Thieving!, A Trainer and Child Reunion!, and Butterfree and Me!.
Ash's 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 Sleep Powder
| A † shows that the move was used recently, unless all moves fit this case or there are fewer than five known moves.