Which episodes in "Pokémon: Indigo League" did these Pokèmon evolve?

Question

Ash's Caterpie → Metapod → Butterfree
James's Magikarp → Gyarados
Jessie's Ekans → Arbok
James's Koffing → Weezing
Ash's Charmander → Charmeleon → Charizard
James's Weepinbell → Victreebel

Answer 1

• Caterpie was first seen in Episode 2, and caught in Episode 3. It evolves into Metapod in Episode 3: Ash Catches a Pokemon.
• Metapod evolves into Butterfree in Episode 4: Challenge of the Samurai.
• Magikarp was bought in Episode 15: Battle Aboard the St. Anne. It evolves into Gyarados in Episode 16: Pokemon Shipwreck
• Ekans and Koffing both evolve in Episode 31: Dig Those Diglett.
• Charmander was caught in Episode 11: Charmander - The Stray Pokemon. It evolves into Charmeleon in Episode 43: The March of the Exeggutor Squad.
• Charmeleon evolves into Charizard in Episode 46: Attack of the Prehistoric Pokemon.
• Weepinbell is an interesting case, as we never actually see it. When we first see it, it has already evolved into Victreebel in Episode 57: The Breeding Centre Sectret. He will later trade it for another Weepinbell, which does then evolve into a Victreebel (Episode 263: Here's Lookin' at You, Elekid), but since that wasn't during the Indigo League, then that is obviously not the one you meant.