I was just playing the virtual console release of Pokemon Red version and my Pikachu tried to evolve after a battle (no thunderstone involved).
Is this some weird glitch?
I was fighting the rival at Pokemon Tower and Pikachu turned level 32 if that matters.
>>27658357
Growlithe has the same index number as a thunderstone.
>>27658373
Example of this.
https://www.youtube.com/watch?v=hqohuVGbhms
>>27658449
>>27658373
OH! Thanks for this explanation!
I had actually seen this happen a long time ago. A friend made the claim that this happened, and he actually could recreate it in-game for me to see.
I was stunned! I thought it was something wrong with his cartridge or something. (I actually haven't thought about this in years.)