Apparently there's Mega Evolution in Pokemon Fire Red Origins

Giving mega evolutions to pokemon that deserve it : r/stunfisk

New] Pokemon Game With Mega Evolution, Radical Red, Z-Moves, Alolan Forms, Dexnav & More!

Now only 20 mega evolution left and nowadays we get random trainers with mega. So which trainer or trainer variant gets remaining mega. Feel free to discuss. : r/PokemonMasters

Pokémon Red and Blue (Video Game) - TV Tropes

Pokemon Fire Red Origins Rival's bugged Mega Evolution

Pokemon 8101 Mega Electrode Pokedex: Evolution, Moves, Location, Stats

This scene from Pokemon Origins quite honestly surpasses every single mega evolution scene in the main anime. : r/pokemonanime

Pokemon 8141 Mega Kabutops Pokedex: Evolution, Moves, Location, Stats

Mega Stones Locations (Part 3) - Pokémon The Last Fire Red V4.3 (GBA)

Pokémon: 20 Mega Evolutions Everyone Uses (That Are Actually Useless)

Could you predict the Canon starter Pokemon every protagonist chose in their games? - Quora

Pokémon FireRed, Chuggaaconroy Wiki

Pokemon Fire Red Origins Rival's bugged Mega Evolution