In HeartGold and SoulSilver, it is possible to evolve Feebas into Milotic, even though Pokémon Super Contests don't exist in the game. This is done by visiting the Haircut brothers in Goldenrod or by talking to Daisy in order to groom Feebas, which not only helps to raise its happiness, but also raises its Beauty. This is not displayed anywhere in-game, and the Pokémon must be viewed in Diamond, Pearl, or Platinum in order for the change to be visible.
copy pasted from bulbapedia
