A Look Back at the Arrowverse's Increasingly Ambitious Crossovers

By most accounts, The CW's week-long "Invasion!" crossover was a roaring success, propelling "Supergirl," "The Flash" and "Arrow" to season-high ratings, and bringing "DC's Legends of Tomorrow" its largest audience ever. The event was, by far, also the Arrowverse's most ambitious event, bringing together the heroes of all four dramas -- more than 30 cast members in all -- to battle alien invaders while also incorporating story elements from each series and celebrating the 100th episode of "Arrow."

That's certainly no small task, yet the producers and writers pulled it off with impressive and entertaining results.

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While crossover episodes are nothing new -- they date back to at least the 1960s -- The CW continues to push the envelope in terms of their difficulty and complexity, especially now that the network has four superhero dramas. From Barry Allen's introduction on "Arrow" in Season Two, to Supergirl's journey to Earth-1 this week, these crossovers demonstrate the ability of the Arrowverse producers to build an interconnected universe that delivers spectacle without ever losing heart. 

Let's take a look back at the crossover episodes that led to "Invasion!," and how The CW managed to make each one bigger and bolder, as the DC Comics television universe expanded. 

Crossover #1: "The Scientist" & "Three Ghosts"

Back in Season Two, "Arrow" began to explore and establish a shared universe in the two-parter, "The Scientist" and "Three Ghosts," which served as a backdoor pilot for "The Flash," which was in development at the time. The audience response to Barry Allen's introduction was so strong that "The Flash" was greenlit shortly thereafter. Whether or not The CW executives and "Arrow's" producers knew it at the time, "The Scientist" and "Three Ghosts" essentially created the blueprints for all crossover arcs that followed.

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Those episodes had to achieve two tasks simultaneously: keep the audience fully invested in the story developments on "Arrow" while creating interest and sympathy for new character Barry Allen. At that point, Barry didn't possess superpowers; he was an ordinary forensic scientist, an unknown quantity in a season that focused on the rise of Deathstroke and his Mirakuru army. At first, Oliver Queen didn't trust Barry (much like how Oliver didn't trust Kara in "Invasion!"), yet Barry proved to be heroic, intelligent and trustworthy; at one point he even saved Oliver's life. By the end of the crossover, Barry was headed home to Central City, just in time to be struck by lighting and become The Flash.

This first crossover kept "Arrow's" primary story moving forward and opened the door to a shared universe with "The Flash." When "The Flash" was greenlit the following summer, a second crossover was announced: "The Flash vs. Arrow," which wouldn't simply take one character from one show to another, but it would feature both casts.

Crossover #2: "Flash vs. Arrow" & "The Brave and the Bold"

A highly anticipated two-night event, "Flash vs. Arrow" saw Oliver, Diggle, Felicity and Roy work alongside Barry, Caitlin, Cisco and Harrison Wells. Each team needed the other's help, first to take down Rainbow Raider in Central City and then Captain Boomerang in Starling City.

The first night of the crossover, "Flash vs. Arrow," provided moments of hilarity while also allowing Barry and Oliver train together. In this episode Barry learned the valuable lesson of using his time wisely -- to case a venue before running into it blindly -- and to trust Oliver's mentorship.

The second episode, "The Brave the Bold," taught Oliver he still had a light inside of him, and that torturing people for information isn't always the answer. Despite being so different from each other, Barry and Oliver and their teams were able to learn from one other. All of that took place against the backdrop of epic scenes that included multiple bomb diffusions, attacks on A.R.G.U.S. and the Arrowcave, and an actual fight between Barry and Oliver. It was a well-executed crossover that maintained the individuality of each show while merging the two with complexity and humor. Watching Diggle throw up and seeing Felicity's blouse catch on fire, both because of Barry carrying them at super-speed, are moments not easily forgotten.

Crossover #3: "Legends of Today" & "Legends of Yesterday"

The third crossover maintained the tradition of back-to-back episodes, but this time it served to set up the spinoff "DC's Legends of Tomorrow." The episodes merged both casts but also introduced the backstory of Hawkgirl, Hawkman and Vandal Savage. These episodes were by far the most complex, and yet, like the previous crossovers, they never lost the focus of either show, nor did they allow the spectacle and threat of Savage to overshadow intimate moments between characters. The episodes also introduced Oliver's son William, showcased more of Cisco's emerging Vibe powers, and gave Barry the opportunity to time travel.

As in previous crossovers, each main character learned a valuable lesson -- one that perhaps they wouldn't have realized on their own. Barry discovered that traveling through time to save his friends was a risk worth taking. Oliver learned not to fight his battles alone, especially when facing an immortal like Savage. Kendra learned who she truly was -- a warrior priestess -- and that hope, not rage, was the key to unlocking her powers.

"Legends of Yesterday" and "Legends of Today" allowed both teams to work together against a common enemy. It was the first time either team had fought an immortal, and they had to rely on the other's strengths to help overcome him. This sentiment of teamwork was carried into last week's "Invasion!," which took twice as many team members to stop the alien Dominators.

Crossover #4: "Invasion!"


Before now, the crossovers unfolded over two nights, on "The Flash" and "Arrow." But "Invasion!" added not one more series but two, doubling the workload that was already tedious to plan and execute. Billed as "Heroes vs. Aliens," it played out across four nights of television on "Supergirl," "The Flash," "Arrow" and "Legends of Tomorrow," and took more than a month to film. Easily The CW's most ambitious crossover yet, the episodes were interconnected and demonstrated the ability of the shows' writers and producers to keep the stories personal while delivering a massive spectacle.

While most of these teams had worked together before, Supergirl was new to this Earth, and she was a worthy teammate. The crossover also happened to fall during "Arrow's" 100th episode, and instead of working around the show's milestone, the writers were able to fit a moving tribute to the characters that the show lost while maintaining the thrilling adventure of an alien invasion.

In addition to assembling this team of Super Friends, the crossover was also able to introduce new elements to the DCTV universe, including an Earth-1 Department of Extranormal Operations and a Hall of Justice. Cisco also built Kara her own teleporter, so she will be able to visit visit more often.

"Invasion!" also addressed the elephant in the room -- Flashpoint -- and its effect on all three of the Earth-1 dramas. At first, everyone was angry at Barry for causing damage to the timeline, but that resentment was washed away when the Dominators demanded The Flash be handed over. The story dealt with Barry's guilt, Martin Stein's daughter, Cisco's anger and even the loss of Diggle's daughter Sara. While the team didn't let Barry off the hook completely, they decided it was more important to stand together than to let Flashpoint separate them. It was this stand of unity that saved the metahumans and the planet from destruction.

All in all, these crossovers are only getting better, and "Invasion!" demonstrates that. No other network has pulled off such an intricate and demanding series of episodes. What the producers have accomplished in assembling this universe compares to what Marvel has done on the big screen, and they deserve credit for not only attempting such a feat but also in executing it beyond audience expectations year after year.

With no signs of slowing down, and thousands of comic book storylines to adapt, The CW has truly just begun to explore the vast world of DC's multiverse.

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