Warning - this article contains major spoilers for The Flash.
Along with an opening salvo by Ben Affleck and a return to glory for Michael Keaton in a supporting role, George Clooney shocked the DCU fandom by coming back as Bruce Wayne in the closing scene of Ezra Miller's solo Flash film.
While his cameo was one of a number of huge names that returned through classic portrayals of DC characters, it left fans with their jaws on the floor considering Clooney's tenuous history with the Caped Crusader.
How Did George Clooney's Batman Return Happen?
According to this report, the cameo came to be over the course of a few weeks, with Clooney screening the movie a couple of times before shooting for half a day in January.
This was also the third different ending to the film that director Andy Muschietti developed through three different leadership regimes at Warner Bros., ending with James Gunn and Peter Safran taking over to help form DC Studios.
Multiple sources tied closely to The Flash revealed that the filmmakers wanted to keep the idea of Barry Allen thinking the world is alright before having the rug pulled out from under him at the last moment.
The crew had also joked earlier in the movie about how many Batmen actors they could possibly get into the story, with Clooney being brought up as a long shot before Gunn and Safran took their shot at him.
Clooney's agent then showed him a mostly-finished cut of The Flash, leading to the Batman & Robin agreeing to join the film after liking what he saw.
The two parties moved to organize a shooting day in January on the Warner Bros. lot where he met up with Ezra Miller on their first day back after discussing the various controversies they had been involved with over the last couple of years.
The shoot was said to be quick and efficient, with Clooney and Miller spending time together in between shoots as the Batman veteran gave the young DC star advice and encouragement.
Will George Clooney Continue as Batman Post-The Flash?
With George Clooney's comeback as Batman becoming one of the biggest spoilers The Flash had to offer, the natural question now is whether this is a one-time thing for the former Batman & Robin leading man.
Even considering that Clooney was such a last-minute addition to the story, rumors have also hinted that this could be just the start of an unexpected return for Clooney as the new era of DC storytelling moves forward.
Outside of Matt Reeves' The Batman - Part II in Gunn's Elseworlds slate, Brave and the Bold will deliver a new take on the Dark Knight that could lend itself to Clooney playing an older version of the hero.
And with Andy Muschietti already in line to direct that movie after working with Clooney on this ending-scene moment, the stage could be set for something new and different to go into development under their watch.
However, despite what the ending of The Flash may appear to tease, Gunn has already debunked any chances of Clooney playing the DCU's Batman, confirming he will instead have a "new actor" under the cowl.
The Flash is now playing in theaters worldwide.