UPDATE 8/2/18 9.05am: Niantic has issued a response to this week's baffling EX Raid battle invitations - and blamed them on a "bug".
The developer says this bug occured when it was implementing changes to the EX Raid system, which it then went on to detail.
There's no mention of the eyebrow-raising invites being sent out on Mewtwo's birthday. Perhaps it was a coincidence...?
Regardless, Niantic has said EX Raids will now take place at larger selection of gyms which meet its "park" criteria, more people will be invited, with higher-rank gym badge holders and regular raiders over the preceeding week preferred.
The bug which affected players getting EX Raid invites to far-flung gyms, or those where they have never raided, is now fixed. Players should, again, only get invited to locations where they have completed a raid recently.
ORIGINAL STORY 7/2/18 10.45am: Last night, Pokémon Go seemingly ripped up its rulebook for how the game invited people to its ultra-exclusive EX Raids - and confused the game's global community in the process.
An EX Raid invitation gives players a chance to battle and capture the legendary creature Mewtwo, and is the most sought-after activity for hardcore Pokémon Go players. Getting a pass, however, is something of a lottery.
In the rules laid down by developer Niantic last year, you have a chance of getting a Mewtwo raid invite if you have recently completed a raid at a nearby gym in a public park.
(That's roughly the rules, anyway - but, in short, the chances of you getting an invite are still low and entirely at the whims of Niantic's shadowy algorithm.)
Last night, those rules were not followed.
Instead of passes for locations people have visited regularly or recently, people were surprised to find invitations to attend at places they had not visited for six months, a year, or had only driven past one time while on holiday.
This fresh round of invites are for EX Raids taking place over this weekend - a much shorter window of warning than usually given.
The requirement to have previously raided at a particular location was also dropped.
There are anecdotes on the game's dedicated Silph Road subreddit of a few people getting invited to EX Raids in other countries.
A handful of local players I know have been invited to raids in other counties, some hundreds of miles away.
That said, a large number of players in my local Discord and Facebook groups appear to have gained an invite - many, many more people than usual. The vast majority of these invites are to locations which are accessible to them.
The town where I live last had an EX Raid in September. Now, there are three within the next few days.
There are positives and negatives to last night's wave of invites, then - especially as many players have grown to dislike the seemingly random, rare nature of EX invitations.
This morning, players are still trying to work out how and why this shake-up occurred. Is this a permanent move, or a one-off? We've asked developer Niantic for more information.
There's a strong argument for this being just a one-off event, however: yesterday was, perhaps not so coincidentally, the birthday of Mewtwo in the original Pokémon games. Niantic did not publicly note this fact - but it feels too much of a coincidence to have not been the reason behind last night's events.