From Bulbapedia, the community-driven Pokémon encyclopedia.
A fateful encounter (Japanese: うんめいてき であい destined meeting) is a flag attached to certain event Pokémon and some event-exclusive wild legendary Pokémon that indicates they were met in a special manner. In Generation III, "fateful encounter" was listed as the encounter location; in Generation IV and on, "fateful encounter" is in the text describing the method of encounter.
However, "fateful encounter" does not always appear in the text of Pokémon with this flag set in Generations III and IV. In Generation III, this flag is set for any Mew and Deoxys received from events, as well as the Deoxys caught on Birth Island and the Mew caught on Faraway Island. Moreover, any Pokémon obtained in Pokémon Colosseum or Pokémon XD will have this special flag set. Without it, it is impossible for these Pokémon to obey the player, even if he or she has obtained all Badges.
In Generation IV, the presence of this flag, from Pokémon Platinum onward, allows for special events to happen if the Pokémon with the "fateful encounter" flag is in the party.
List of in-game events activated by fateful encounter Pokémon
- In Pokémon Diamond and Pearl, the Shaymin that is captured in the Flower Paradise will not be a fateful encounter Shaymin, while in Pokémon Platinum, it will be. This was likely implemented due to the tweaking and Surf glitches, which allow access to Shaymin in Diamond and Pearl, while this was removed in Platinum. Due to the way receipt and use of the Gracidea is programmed, if the Platinum Shaymin were not given this status, despite being able to be legitimately obtained with Oak's Letter, it would not be able to transform into Sky Forme.
- It was once believed that a fateful encounter flag was needed to be set on a Jirachi in order to activate the Night Sky's Edge Pokéwalker route; indeed, events where such Jirachi were distributed advertised such an unlockable. However, it was later discovered that all Jirachi are capable of unlocking the route even without the fateful encounter flag.