A redditor named DaRk_ViVi reported catching a shiny Ditto from an encounter with shiny Drowzee. Previously, it was believed that shiny Pokémon cannot turn into Ditto, only regular versions of Ditto disguises.
Now, before you go all out shiny checking anything that Ditto can disguise into, please be aware that Vivi’s catch has some unique properties which indicate it’s a buggy edge case, rather than a change in the in-game mechanics.
Vivi encountered a shiny Drowzee from the guaranteed daily spawn encounter, rather than a regular wild encounter, and the current running theory is that Niantic forgot to enforce the limits in the daily spawn encounter.
It is unclear at this moment if the mechanic has changed, but it seems unlikely to us. Vivi’s report is the only report to date, which seems reasonable given the daily spawn pool and the chance to get a shiny.
However, there is a slight chance Niantic is pulling something here, given that we’re in the Season of Mischief currently. Be sure to check up on the Misunderstood Mischief Research Tasks and Rewards while you’re at it.
Shiny Ditto mechanics
As we wrote earlier this year in our How Does Shiny Ditto Work in Pokémon GO article, shiny Pokémon cannot turn into a shiny Ditto when caught – regularly. Ditto can be disguised as a regular version of the Pokémon, and become shiny when caught, but it can’t go the other way around/
As many of the Ditto transformations have shiny forms, it would be misleading (and somewhat saddening perhaps) for players to catch a shiny Gastly only for it to transform into a shiny Ditto.