As you'll no doubt be aware by now, The Flash features several major cameos from previously established and Multiversal characters. Most of these have been leaked, but below you'll find a more detailed breakdown of how they factor into the film.
Major spoilers from this point on.
The first familiar face from the previous DCEU era we see is Jeremy Irons, who makes a welcome return as Alfred Pennyworth. Batman's loyal ally contacts Barry Allen at the start of the movie to let him know about a dangerous situation at a hospital, and stays on the line while the Scarlet Speedster saves a bunch of animated babies.
Next up is Gal Gadot as Wonder Woman. Diana's appearance was said to be cut from the final version of the movie, but she shows up to lend a hand to Barry and Ben Affleck's Batman, sticking around just long enough for a pretty awful Lasso of Truth gag.
The cameos stop for a while until the Flash enters the Speed-Force in the final act, and we get a bunch of CGI takes on alternate reality incarnations of some legendary DC heroes. Adam West's Batman is glimpsed, as well as George Reeves' classic Superman, and Teddy Sears' Flash. And, in what will likely be the most talked-about sequences, we also see Christopher Reeves as Superman alongside Helen Slater's Supergirl, and Nicolas Cage as the Supes who almost was in Tim Burton's defunct Superman Lives battling a giant spider.
Then, right at the end when Barry returns to what he assumes to be his own reality, Bruce Wayne calls him up for a meet - but the version of the Dark Knight that steps out of the car is not played by Affleck or Keaton, but George Clooney's from Batman and Robin.
Finally, a very drunk Aquaman (Jason Momoa) stumbles out of a bar with Allen in the only post-credits scene. He falls into a puddle and stays there despite his fellow Justice Leaguer reminding him that he was going to sleep on his couch. Arthur gives Barry his Atlantean ring, and tells him to go find more beer... fast!
Have you been to see The Flash yet? If not, do you plan on checking it out this weekend?
"Directed by Andy Muschietti, The Flash features Barry Allen traveling back in time in order to change events of the past. But when his attempt to save his family inadvertently alters the future, Barry becomes trapped in a reality in which General Zod has returned, threatening annihilation, and there are no Super Heroes to help. That is, unless Barry can coax a very different Batman out of retirement and rescue an imprisoned Kryptonian…albeit not the one he’s looking for.
Ultimately, to save the world that he is in and return to the future that he knows, Barry’s only hope is to race for his life. But will making the ultimate sacrifice be enough to reset the universe?"
The Flash is produced by Barbara Muschietti and Michael Disco, with a screenplay by Christina Hodson, and a screen story by John Francis Daley & Jonathan Goldstein and Joby Harold, based on characters from DC. Warner Bros. Pictures presents a Double Dream/a Disco Factory production of an Andy Muschietti film.