Here are the memories Ash, Jessie, James, and Dawn have had before they released a Pokémon, gave them to someone else for training, or almost released a pokémon and why they released them, gave them to someone else, or almost released them.
Pokémon that have been released
* Ash's memories of Butterfree in "Bye Bye Butterfree"
1. Ash catching Butterfree when he was a Caterpie in "Ash Catches a Pokémon"
2. Caterpie evolving into Metapod in "Ash Catches a Pokémon"
3. Meatpod evolving into a Butterfree in "Challenge of the Samurai"
4. Ash and Butterfree battling against Misty's Staryu in "The...