When a Pokémon with Costar enters the battle, it copies an ally's stat stages for itself.
Costar
When the Pokémon enters a battle, it copies an ally's stat changes.
Pokémon with the Costar ability
#973
Flamigo
flying
fighting
HP: 82 Atk: 115 Def: 74
Sp.Atk: 75 Sp.Def: 64 Speed: 90
Total: 500