Ep 18. World's Finest

Kara Danvers, also known as Supergirl, finds herself in a Gotham City unfamiliar to her in the eighteenth episode of the first season, titled "World's Finest". She crosses paths with the city's caped crusader, Batman's alter-ego, Bruce Wayne's distant cousin, and alter ego of Wayne Enterprises' owner, Kate Kane - also known as Batwoman.

As soon as Supergirl lands in Gotham, she meets a young man named Barry Allen. Barry is actually The Flash, a costumed vigilante from Central City who received his superhuman speed after being struck by an unknown source of energy. He is momentarily lost in a parallel universe while trying to break a time barrier which ends up crossing over to Earth-38. After quickly finding common ground, Barry Allen and Kara begin working together to take down a common foe, Siobhan Smythe [the Silver Banshee], and Livewire, in Gotham's underground.

But while he's there, Barry finds himself struggling with the fact that he can't travel back to his friends, while Kara battles with the idea of letting go of her crush on James Olsen. Throughout the episode, the two heroes work together in a mindboggling display of acrobatics and firepower while learning about each other's past and current battles. Meanwhile, back in National City, James and Winn try to track down Kara in hopes of helping her return safely home.

The episode adeptly juxtaposes two cities that might as well be two separate worlds. Supergirl is used to a world where she is the sole protector of National City and where people know about the existence of extraterrestrial life. In Gotham, she finds herself in a place where fear rules and the focus is mostly on Batman. The episode fleshes out these two worlds smartly without losing sight of the characters at the center of it all.

The most satisfying part of "World's Finest" is the camaraderie that develops between Supergirl and The Flash, who prove to be a great team. They enjoy each other's company and seem to intuitively understand what one another's strengths and weaknesses are. Together, they battle against Siobhan Smythe's banshee scream and Livewire's electricity.

While the episode is light on the villains, it makes up for it with the interactions between the two titular heroes. It’s amazing how well Barry Allen and Kara Danvers bond. There are a lot of fish-out-of-water antics played up initially, but the two superheroes soon develop a natural chemistry. There's a lovely scene in which they fly to the top of a building to survey Gotham while sharing a bag of Cracker Jacks, and another in which they run races to test who's faster.

There are a few fun tidbits that fans will appreciate- there's a reference to Ferris Air (test pilot Hal Jordan of Air Force One would later go on to become the green lantern), as well as a mention of the dearly departed Superman when Barry marvels at how much Kara reminds him of his friend on his Earth. The two actors are comfortable with each other and manage to elevate the quality of their banter. Grant Gustin especially seems to be relishing the chance to shed the broody persona that The Flash sometimes takes on. It's genuinely delightful to see Barry happy and relaxed for once, smiling and joking around with Kara.

The downside of "World's Finest" is that it's mostly a standalone episode, albeit one that has a significant impact on Kara's character development. There are few surprises in the story, and while the villains are cool, they don't create the sense of urgency or tension that many other Supergirl episodes manage to achieve. The conflict is largely resolved by the end of the episode, so it's not a huge game-changer in terms of the overall season.

However, it is a great fun crossover that offers a refreshing change from the oppressive grittiness that often defines Gotham and National City. It's refreshing to see two heroes genuinely get along in a story that has no agenda other than to entertain audiences with fun action scenes.

Overall, "World's Finest" is a charming, entertaining episode of Supergirl that offers up a fun crossover with The Flash. It's not the most memorable installment of the season but it's definitely worth watching for fans of either show or the DC Universe as a whole.