SPOILERS FOLLOW!
The Batman doesn't feature a post-credits scene, but there is a URL pointing fans to https://www.rataalada.com/. Up until a few days ago, it still featured a few riddles that would unlock a video teasing Thomas Wayne's involvement in the corruption Gotham City has fallen victim to.
However, it's just received a potentially significant update.
With The Batman now playing in theaters, a visit to the site currently sees a sequence play with the website being rerouted through various networks, including one belonging to Arkham State Hospital. From there, you'll be taken to a page that features a link titled "[CLICK FOR REWARD]." A countdown below currently sits at 27% and is slowly updating; what arrives at 100% remains to be seen.
The aforementioned link leads us to a coded message:
Intriguing, eh? The Batman director Matt Reeves has talked about releasing a deleted scene featuring the World's Greatest Detective confronting The Joker in Arkham, so perhaps that's what we'll see? A sequel announcement is also possible, though it might be something a little less exciting! The fact that it's been updated to coincide with the movie's release could be significant, however.
We'll obviously keep an eye on that countdown and bring you updates as soon as we have them.
The Batman is now playing in theaters worldwide.