In its first year, the "Arrowverse" crossover between The Flash and Arrow was little more than two disconnected episodes that had guest stars swinging back and forth to fight bad guys and discuss feelings. Last year, the crossover set the stage for the launch of DC's Legends of Tomorrow, functioning as a backdoor pilot while still continuing some storylines in Flash or Arrow -- like, ugh, Oliver's (Stephen Amell) baby drama.

This year, there's no new series to set up, and since Supergirl isn't a part of Earth-1 -- the show still kicks it Earth-38 style -- all that was required to make it a full crossover event between The CW's four show was creating a rift between worlds and grabbing Kara (Melissa Benoist). Boom. Done. The result, at least based on the first part of "Invasion!" (Arrow and Legends of Tomorrow episodes this week share the same title) here in The Flash, is a very different sort of crossover, one that calls to mind comic book annuals.

For those who don't read comic books, the concept is pretty simple. Annuals were published once a year, and they were normally just digests of earlier issues, but DC and Marvel both realized there was an opportunity to tell bigger, splashier stories every year. The annuals basically became event issues for their respective titles. For instance, Peter Parker and Mary Jane Watson tied the knot in an annual. Annuals are less common than they once were in the '80s and '90s. If they happen, they're normally telling multiple stories, and they don't even happen every year.

"Flashpoint" comes back to haunt Barry in a big way

Because of their super-sized nature, annuals were also good ways to feature comic book universe-spanning crossovers while still having room to focus on each title's own storylines. They gave real bang for their ever-increasingly pricy buck. The "Arrowverse" crossover this year feels like it's operating in that tradition: A big storyline of aliens coming to Earth for soon-to-be-revealed reasons, while not sacrificing storylines from the individual shows. Indeed, on The Flash, they're even taking the opportunity to further those storylines a bit.

On the Flash side of things, the big takeaway was that now everyone of established significance to the "Arrowverse" -- apologies to Amaya (Maisie Richardson-Sellers) and Nate (Nick Zano), who were stuck on the Waverider, and Earth-38 was probably unaffected -- knows that Barry (Grant Gustin) mucked with their lives thanks to the creation of the Flashpoint timeline. It appropriately rattled everyone who cared -- Mick (Dominic Purcell) did not seem to mind -- and led to a lecture about the ramifications of time travel from Sara (Caity Lotz) and Ray (Brandon Routh), and disapproving looks from Martin (Victor Garber).

The result was the same as it has been on Flash this season: Barry knowing he screwed up and trying to make up for things however he can. In this case, it meant forming and leading a team of superheroes to stop a bunch of scary aliens from taking over the world. While the non-Flash regulars came around by the end (getting mind-controlled by a bunch of aliens will put things into perspective, or, as Oliver said, "One sci-fi problem at a time") it still didn't do anything to thaw Barry's chilly relationship with Cisco (Carlos Valdes), though Caitlin (Danielle Panabaker) seemed to have come to terms with Flashpoint enough to suggest getting drinks as a trio.

So while Barry grappled with failings as a hero in ways that continue to reverberate across the "Arrowverse," there was still room to deal with Flash-specific issues, namely Wally's (Keiynan Lonsdale) speed. The rest of the Wests were united in their refusal to allow Wally into the field and assume the Kid Flash mantle in the current timeline, but Wally's not the best at listening to others, as we know from last season. So, in between helping out Barry and Oliver fight mind-controlled allies, he enlisted HR (Tom Cavanagh) as his secret mentor. Because what could possibly go wrong with a Wells as a mentor?

Even with all this, there was still room for Martin to find out that he now has a daughter, though whether that's due to Flashpoint or his actions in 1987 remains unknown, though it seems likelier to be the latter than the former. In addition to that bit of Legends of Tomorrow development, we finally got to hear the entirety of Future Barry's message to Martin and Jax (Franz Drameh), and it was about Flashpoint, but may have been about something else, too.

Despite not being actually super-sized, The Flash's "Invasion!" still felt like a super-sized episode because of everything in it on a plot level, and then all the ultra-cool superhero vs. superhero battling that took place at the end of the episode. And since the crossover isn't setting up any other shows, just continuing storylines, there's lots of room to do an episode like this, or something special for Arrow's installment, which happens to be the show's 100th episode, itself an occasion for annual-like story.

For the first time, the crossover, and indeed, the "Arrowverse" as a whole, felt well-connected without feeling forced. Hopefully they can keep it going all week, and repeat it next year.

The crossover event continues Wednesday night at 8/7c with the 100th episode of Arrow.

The Flash airs Tuesdays at 8/7c on The CW.

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