A crossover between the two series was announced in July 2014, after Barry Allen had been introduced in Arrow's second season ahead of the debut of The Flash.

Later, Oliver informs Barry that he and his team are in Central City tracking down intel on a killer who uses lethal steel boomerangs.

Eddie continues to persuade his superiors to form a task force unit to capture the Flash, expressing his zero tolerance for vigilantes.

Oliver advises him to stay away from Iris West, with whom Barry is in love, for a while, because men with secret identities as vigilantes never succeed romantically.

Caitlin Snow and Cisco Ramon arrive in Starling City to help Felicity Smoak investigate Sara Lance's homicidal murderer.

[9] The crossover was originally planned as the seventh episodes of each series, but was pushed back due to the large amount of work needed to accomplish it.

"[10] Greg Berlanti, creator and executive producer on both series, explained that "crossovers are part of [the characters'] DNA, ... and if we waited ..., then we would be depriving the audience of something we all wanted to see".

[16] At the end of the episode, Robbie Amell, who played Ronnie Raymond—Caitlin's former fiancée presumed dead after the particle accelerator explosion—appears as Firestorm using his powers.

[18][19] Berlanti drew inspiration from science fiction action television series The Six Million Dollar Man and The Bionic Woman for the story, while Kreisberg took his cues from the final episode of the fourth series of Doctor Who, titled "Journey's End", a crossover featuring the characters of spin-off shows Torchwood and The Sarah Jane Adventures.

[13] Kreisberg revealed that the writers' rooms for both shows were merged while working on the scripts for the episodes, similar to "throwing two casts together".

Because this was the first time Stephen Amell's character fought someone with superpowers, he had to change the way he performed stunts to accommodate the special effects.

[29] The "Flash vs. Arrow" crossover episodes were shown at an exclusive fan screening at the Crest Theatre in Westwood, Los Angeles on November 22, 2014.

[30] Afterwards, Amell, Gustin, David Ramsey, Emily Bett Rickards, Danielle Panabaker and Carlos Valdes were joined by executive producers Berlanti, Kreisberg and Guggenheim for a Q&A panel.

Its viewership grew by 46% and its 18-49 rating by 56% over the previous episode, "Draw Back Your Bow",[45] and helped contribute to the most watched Wednesday on The CW in more than two years.

called the crossover episodes "fun" noting that "plenty of show-specific plot stuff was advanced without spelling it out for newbies.

The website's critical consensus reads, "The Flash pulls off a thrilling crossover with its sibling series, Arrow, by skillfully blending the two shows' disparate tones and showcasing its dueling superheroes' complementing strengths.

Von Doviak complimented writers Greg Berlanti and Andrew Kreisberg, and director Glen Winter, for tackling the "clashing tones of the two shows" and the different personalities of their main characters, and "weaving...[them]... into the fabric of the episode".

He also highlighted the fight scene between the Flash and Arrow, saying "It's a well-choreographed battle, with each hero appearing to have the upper hand at various points and clever bits of one-upmanship.

He felt that Arrow's "knocks" made the point that "Barry's superpowers are an amazing gift ... he must hone and perfect to become a truly heroic character."

Trumbore also "loved how Arrow's attention to detail and commitment to bettering himself through training clashed with Flash's carefree style and almost lazy attitude when it came to beating up baddies".

She noted this episode demonstrated how comic book ideas "can translate to the small screen if done with this much care, joy and enthusiasm".

Given the "hype" she admired, and was "surprised" by the fact that even "with a little added Oliver, Felicity and Diggle thrown in," the crossover was not the focus of the whole episode.

The website's critical consensus reads, "This Arrowverse crossover episode manages to entertain while posing thoughtful questions about morality – and all without getting bogged down in meta references.

Schedeen enjoyed the teams continuing to cross paths, the drama between Barry and Ollie, and "the balance between light and dark [the crossover] needed".

Club gave the episode an "A−", saying it "..can just cut loose and have some ['effortless'] fun for an hour," noting that Barry "is one of the only characters able to call Oliver out on his more mopey strains of bullshit".

Barry Allen's approach to crimefighting is effervescent and "carefree" reflecting "Central City's cutting-edge technology" and "squeaky-clean streets".

"'The Brave and the Bold'... felt... like a crossover episode ... servic[ing] Oliver's identity issues and character development."

Agrad felt that "Cisco fanboying all over the place" is "fun" and Captain Boomerang is a "most formidable and compelling opponent because he uses strategy and plans multiple steps ahead".

He saw it as season's "strongest" Arrow episode, and "a great conclusion to the very successful Arrow/The Flash crossover" where in an "emotionally charged hour...all the elements come together with remarkable dexterity".

The Flash's smooth moves versus Arrow's strength and stratagem made for a thrilling tango that lived up to the hype.