On their way to Saffron City, Ash, Misty, and Brock come to the top of a high cliff. Brock tells the others that the cliff should lead them to Saffron City. Ash sees a big group of Butterfree in the sky. Brock says that it is the time of the year when all of the Butterfrees mate.
They rent a hot air balloon and they follow the group of Buttefree. Ash sends out his Butterfree so it can find a mate but it struggles to get attenion from the other Butterfree. Ash's Butterfree soon falls in love with a pink Butterfree. Sadly, the pink Butterfree rejects Ash's Butterfree. It slaps Ash's Butterfree with its wing. Ash's Butterfree flies away crying to a nearby forest.
Soon, Ash and his friends find Butterfree in the forest. Ash tells Butterfree to show its strength to the pink Butterfree to win its heart. To make it look better, Brock ties a yellow scarf around its neck.
They soon return to the sky with Butterfree, having gotten its confidence back. Ash's Butterfree fails to impress the pink Butterfree with a Whirlwind and a Tackle attack. Team Rocket arrives in a helicopter. They say their motto and then they capture all of the Butterfree, except Ash's Butterfree, with a net. Ash's Butterfree tries to break the glass on the helicopter by using Tackle, but it doesn't work. It then tries to use Stun Spore to stop them, but it doesn't work either. Ash is about to recall Butterfree and use Pidgeotto instead, but Misty stops him by saying he might hurt Butterfree's feelings. Team Rocket flees and Butterfree and Ash and his friends follow them to a warehouse in a canyon.
Ash and his friends break in the warehouse through a window while Jessie and James count all the Butterfree they caught. Misty sends out Starmie and tells it to use Tackle to chase Team Rocket while Butterfree starts to Tackle the net holding all of the other Butterfree. After many tries, Butterfree finally breaks the net open. Jessie whacks Starmie with a hammer, but Misty revives it by spraying it with water. Brock opens up the doors and the Butterfree fly out the doors. Team Rocket frantically tries to catch them all with nets., but they fail. Ash's Butterfree, worn out from breaking the net open, is still inside. The pink Butterfree approches it, impressed by its determination. James tries to catch it, but Ash's Butterfree knocks the net away, making the pink Butterfree blush.
Team Rocket tries to catch the Butterfree by getting back into their helicopter. Ash and his friends follow them in their rented balloon and they quickly find them. The pink Butterfree watches as Ash's Butterfree flies to the helicopter with Pikachu riding it. Pikachu jumps on the helicopter and destroys it with an electric attack. Team Rocket falls into a canyon, disappearing into the darkness. The pink Butterfree does a courtship dance to Ash's Butterfree and Ash's Butterfree accepts it.
Back at the cliff, Ash sadly says good bye to his Butterfree and its new mate. As they fly into the sunset, Ash remembers catching it as a Caterpie, it evolving into a Metapod and then a Butterfree. As his Butterfree is almost out of sight Ash wishes it good luck.
- In the scene with Team Rocket falling into the canyon, Jessie's lipstick and nose are missing.
- This is the first episode where Team Rocket's Motto gets ripped off.
- This is also the first episode where a main character releases a Pokémon.
- SPOILER: This the first episode where Ash releases a Pokémon.
- This episode is the first one where Team Rocket have thought's about Boss Fantasies - Where they think about stealing Pokémon and giving them to Giovanni.
- The English Title is a play on the musical Bye Bye Birdie.
- This episode introduces the concept of Different Colored Pokémon. In this case, a pink Butterfree.
- This episode contains a montage of Ash's Butterfree, from when he first caught it as a Caterpie, to it's evolution into Metapod, to its final evolution of Butterfree and every battle they were in. The Pokémon theme was played in the background when Ash said goodbye to Butterfree.
- The "Who's that Pokémon?" in this episode is Butterfree.
- The song played in the beginning of the Butterfree Montage is called "Tears After Cloudy Weather."
- This is one of the few episodes where Team Rocket doesn't try to steal Ash's Pikachu, instead they attempt to steal another Pokemon species (failing as usual).
- The star that usually appears when Team Rocket blasts off makes it's first appearance since "The Water Flowers of Cerulean City" (not counting "Beauty and the Beach").
- When Ash congratulates Pikachu for getting rid of Team Rocket, Pikachu says "Big Pikachu".
- Ash doesn't use his pokedex in this episode.
- Ash: "Prepare for trouble."
Misty: "And you can make it triple."
Brock: "To protect the world from devastation."
Ash and Misty: "To unite all peoples within our nation."
Jessie: "This was just..."
James: "...Too good..."
Meowth: "...To last."
Watch this and other episodes: Pokémon Episode 21: Bye Bye Butterfree