In a rather interesting move, Niantic released the research for the upcoming Kanto Throwback to select players, allowing them to complete it without any sort of an announcement. While many who received it managed to complete the tasks, Niantic later announced that the release was a mistake, and that those who have already received the tasks will not be able to complete them again on their official release.
Trainers, research was released to some Trainers ahead of schedule. The event details will be released in the near future, meanwhile Trainers who received this research can complete it now but won't receive it again. Sorry for the confusion!
— Niantic Support (@NianticHelp) April 27, 2020
Apparently, the star of this research is Psystrike Mewtwo, which can be shiny according to reports.
We've added the Kanto Throwback to our Research page, though it may change before the official release. Either way, it's exciting to see another new way to catch such a powerful Pokemon!