Ho-Oh appears above Ash in the first episode of the Pokémon anime.
At the end of “Pokémon, I Choose You!”, Ash sees a large, colorful bird Pokémon flying across a rainbow-filled sky. The broadcast does not initially identify it by name, making the brief sighting an early mystery for viewers. The Pokémon was later established as Ho-Oh, a Legendary Pokémon associated with rainbows and resurrection.
Ho-Oh was especially notable because it had not yet been obtainable in the first Pokémon games when the episode premiered. The anime therefore gave audiences an early glimpse of a Pokémon connected to the second generation, which would arrive later with Pokémon Gold and Silver.
The scene is sometimes confused with Lugia, another major Legendary Pokémon from the Johto era. Lugia became prominent in Pokémon the Movie 2000, while Ho-Oh is the mysterious flying Pokémon seen by Ash in the anime’s opening episode.