Synonyms that are in the dictionary are marked in green. Synonyms that are not in the dictionary are marked in red.
Antonyms that are in the dictionary are marked in green. Antonyms that are not in the dictionary are marked in red.
A trade is considered special if it includes a Pokemon or Pokemon Form that's not already in the players' Pokedex, a Legendary Pokemon, a Shiny Pokemon, or an Ultra Beast.
Source: https://gamerant.com/pokemon-go-how-to-catch-mr-mime/
Various wild spawns lurk during the event too, with players having an opportunity to get several Shiny Pokemon.