Part 4 of the event, which technically took place during an episode of Arrow, did something that we never thought possible. Sure, this crossover has gone the distance and put everyone from Robert Wuhl to the Titans in the mix, but things have officially gone to the next level.
**SPOILER WARNING: From this point forward, there are major spoilers for Part 4 of Crisis on Infinite Earths. Seriously, major. If you have not watched and do not want to be spoiled, get out now. We cannot stress this enough. Run, Barry, RUN.**
So... how do we put this? Ezra Miller, welcome to the Arrowverse, or Arrowverse, welcome to the DCEU?
Ezra Miller, who plays The Flash in the films of the DCEU, appeared in Part 4 of Crisis on Infinite Earths. He appeared as Barry Allen, and this officially links the shows of the Arrowverse to the movies of the DCEU. We... we just... they should've sent a poet.
It all went down after Grant Gustin's Barry Allen found himself in STAR Labs after a chase with the Anti-Monitor. That's where he met Miller's Allen, and Miller began things with a joke, asking if Gustin's Allen was cosplaying as him. Gustin then called Miller's Allen by the name "The Flash," which is a name that was never uttered during Miller's appearances in Justice League, etc.
Miller's Allen then seems to fade away, and says, "I told Victor this was possible." He is surely referring to Victor Stone, aka Cyborg (Ray Fisher), whom he met and worked with in Justice League.
Thus it became canon that the Arrowverse does indeed take place in a universe that is parallel to the movies of the DCEU. According to IGN, Miller told MTV in 2015 that he wanted to interact with Gustin's Barry Allen. Well, his wish has been Granted. Not only that, but Miller's version of the character now has an origin for his superhero name, and it was given to him on the small screen.
The real kick here? There's still one part of Crisis on Infinite Earths left. For all we know, the gang from Riverdale could show up alongside the entire cast of Ad Astra and, we don't know, Val Kilmer... not playing Batman, though. He'd be playing Madmartigan. (Note: this did not happen in Part 5.)
Crisis on Infinite Earths has ended, but nothing in the Arrowverse, the DCEU, or Riverdale will ever be the same...