Towards the end of “The Batman,” after Riddler has been escorted to his private cell at Arkham Asylum, he discovers that he isn’t exactly enjoying his solitude. Maybe he misses his Internet friends. Perhaps he’s mourning his non-existent friendship with the Batman. Anyway, the Riddler is pretty unhappy about his situation, until a fellow prisoner indulges him in the one thing he loves most: riddles. What’s more interesting is that we don’t clearly see the person behind the voice — just the side of his face through a small window in the cell door. The answer to the riddle he asks, of course, is “friend,” teasing that the Riddler has a dangerous new mind to collaborate with.

This version of the Joker is played by actor Barry Keoghan (“Eternals” and “Killing of a Sacred Deer”), who was previously announced to have been cast as police officer Stanley Merkel in “The Batman.” In an interview with IGN, the director shared that he devised a plan to conceal Barry Keoghan’s true association with the film — and even shot fake scenes to protect the reveal (candid set photos showed Keoghan dressed as a cop). Matt Reeves was worried fans would speculate about the film exploring the Joker, so he did his best to keep it a surprise.

“When you’re making a movie like this, you want it to be different, you want people to feel like they’re having a special experience. And then for me, when you’re going to the cinema you want some level of surprise. I think one of the things I was worried about was speculation while we were making the movie, that we would be exploring the character that we ended up exploring. So we started thinking what we could do to throw people off that scent. This idea of making him Stanley Merkel was exactly that, because the police force is actually a big part of the story so it seemed credible that we could be doing that.”

When the credits roll, you’ll see that Keoghan is credited as “Unknown Arkham Prisoner” — which fits with the enigmatic nature of the scene, and also probably went some way towards helping keep the true nature of Keoghan’s character a secret. Now, the truth has been unmasked.

“The Batman” is in theaters.