Yeah, this is rumor and therefore must be taken lightly.
As per a report over at CBR, and according to the actor’s brother Eric Keoghan, the since-erased post read:
“So it’s finally out My Brother playing the JOKER in the new Batman Unreal Stuff.”
While Barry Keoghan is currently in cinemas as part of Marvel’s Eternals playing mind-controlling Druig, back in 2020 the actor was confirmed as being part of the cast of the upcoming Matt Reeves movie The Batman.
At the time, Warner Bros. announced that the star will be playing Stanley Merkel, an officer in the Gotham City Police Department who originally appeared in a 1987 Batman story as the partner of Jim Gordon.
In comic book canon, Merkel met an end at the hands of Sofia Falcone aka Hangman. It looks like his character could be taken in a different direction to his on-the-page counterpart in The Batman.
There has been more than one suggestion that the character we have been led to believe is The Riddler will actually turn out be a red herring, as so far the trailers have been careful not to give a look at the face of the main villain of The Batman.
So there is still a hanging question over whether the ambiguity of the character’s appearance is significant to the secrets being kept by the movie.
The Batman has seen numerous delays due to the Covid pandemic, but it will finally debut in theaters on March 4th.