Magikarp evolves into Gyarados at level 20, and this has remained consistent since the very first Pokémon games in Generation 1.

Gastly, the Ghost/Poison-type Pokémon numbered #092 in the National Pokédex, evolves into Haunter at level 25 and then into Gengar through trading.

Abra evolves into Kadabra at level 16, and Kadabra then evolves into Alakazam through trading with another player.

Machop evolves into Machoke at Level 28, and Machoke then evolves into Machamp through trading with another player.

Psyduck evolves into Golduck at Level 33. This straightforward level-based evolution applies across all mainline Pokemon games, from the original Red and...

Meowth evolves into Persian at level 28 through standard level-up evolution, but this only applies to the original Kantonian form.

Jigglypuff evolves into Wigglytuff when exposed to a Moon Stone, and it can also evolve from Igglybuff when that baby form reaches high friendship with...

Squirtle evolves into Wartortle at Level 16, and Wartortle then evolves into Blastoise at Level 36.

Bulbasaur evolves into Ivysaur at level 16, and Ivysaur subsequently evolves into Venusaur at level 32.

Charmander evolves into Charmeleon at Level 16, and Charmeleon then evolves into Charizard at Level 36.