We knew we were getting all the cameos in Crisis on Infinite Earths, but holy crap, we didn't think we were getting this one! In a shocking move, the Arrow episode of the crossover featured a cameo from Ezra Miller's Justice League version of the Flash, who showed up to interact with The Flash's Barry Allen (Grant Gustin).

This is the first time the DC Cinematic Universe has crossed over in such a major way with the TV brand, and especially within the Arrowverse. There has notoriously been an impenetrable wall between the films and the TV shows, but that seems to have been broken down — at least for the sake of this one episode.

The scene came about thanks to the narrative device known as the Speed Force, in which Barry has frequently seen visions of important people in his life. On a mission from Oliver (Stephen Amell), Barry set out to find the Seven Paragons, who had all been lost in the Speed Force. His first stop on his quest saw him take a wrong turn to S.T.A.R. Labs, where he encountered Miller's version of the Flash.

Discover Your New Favorite Show: Watch This Now!

They shared a completely trippy moment when they realized they were both versions of Barry Allen, and they even took the time to comment on each others' super suits. Miller's Barry complimented his counterpart's "comfy" version of the suit that looked very breathable. In exchange, Gustin's Barry was impressed with the more metallic-looking Flash suit, saying it looked "safe."

The scene wrapped up with Miller's Flash fading out of view, but not before remarking that he told Victor something like this was possible. We can only assume he was referring to Victor Stone, who played Cyborg in Justice League.

"I was really working hand-in-hand with Jim [Lee, Chief Creative Officer of DC Comics]," Arrow boss Marc Guggenheim told Entertainment Weekly of the scene. "From the moment we found out that this was a possibility, to once we knew Grant Gustin was cool and on board with it, and Ezra was on board with it, I would send drafts of the scene to both Jim Lee and [DC Entertainment's film VP] Adam Schlagman and we would just go back and forth. The trick with the scene is that I didn't want to — and they didn't want me to — do anything that stepped on the toes of the Flashpoint movie that they're developing. So, we really worked hand-in-hand. Jim was really great about just making sure that all the parties were talking to each other, that nothing was getting stalled. He was a cheerleader when he needed to be, a diplomat when he needed to be. He really stepped up in every way one could do it. His enthusiasm really helped make this possible."

This crossover is truly one for the record books!

Everything We Know About the Crisis on Infinite Earths Arrowverse Crossover

Supergirl and Batwoman return Sunday, Jan. 19 at 8/7c and 9/8c on The CW. Arrow and DC's Legends of Tomorrow return Tuesday, Jan. 21 at 8/7c on 9/8c on The CW. The Flash will return Tuesday, Feb. 4 at 8/7c on The CW.

Ezra Miller, <em>Justice League</em>Ezra Miller, Justice League

(Disclosure: TV Guide is owned by CBS Interactive, a division of ViacomCBS.)