Level up Mime Jr. while it knows Mimic
In Pokémon Sword and Shield, level up Mime Jr. while it knows Mimic to evolve into Mr. Mime
In Pokémon Brilliant Diamond and Shining Pearl, level up Mime Jr. while it knows Mimic to evolve into Mr. Mime
In Pokémon Legends: Arceus, Mime Jr. evolves into Mr. Mime by using a Rare Candy or leveling up after learning Mimic
In games where Mime Jr. cannot learn Mimic, it does not evolve by level-up until it does