>>56149005Celebi, Jirachi, Manaphy/Phione, Shaymin, and Victini would all be Fairy-types if that type existed back then. All of them (minus the Gen 4 ones) were given the Psychic-type instead since it is the next best thing. Manaphy and Phione are even in the Fairy Egg Group.
The reason why Manaphy (mana fae) and Shaymin were an exception is probably because there were too many legendary Psychic-types already in Gen 4 alone.
Even the other Gen 4 Psychic legendaries may have gotten that type because it was the closest to a fairy type. Cresselia is associated with the full moon, and the Lake Guardians were named after pixies, sprites, and elves.