They just released shiny mew but to get it you had to pay £15 for an event they were doing, which then got you the research for the shiny Mew after. And they weren’t easy tasks either, it’s stuff like visit 151 different Pokestops, catch 151 different mons, and stuff that would take you a while to do.
also before this they had put a version on Mr Mime behind a paid research too.