Very good, except for throwing it out at the end and pressing B to stop it's evolution.
Would've been cooler if the Kakuna somehow didn't want to evolve and held on to some of it's previous traits, but you wanted it to evolve so it could be more powerful than before, but due to your greed, the Kakuna is now a freak of nature.
The sprite was very high quality and looked almost exactly like something you'd see in Red and Blue.
Still, good job! It made for an interesting read and the sprite was pretty sweet, too.
EDIT: Or if it said "KAKUNA is trying to RESIST" "RESIST" "RESIST" "KAKUNA is IN PAIN" and then "3... 2... 1... POOF! KAKUNA has forgotten EVOLUTION!"
EDIT 2: And instead of the normal fanfare playing, a distorted cry that sounds like a mix between Kakuna's and Beedrill's plays.