Half the fun of building a shared superhero universe is the crossovers that crop up as a result. We've already seen plenty of interplay between The Flash and Arrow this fall, but this episode marked the first full-fledged crossover between the two shows. "Flash vs. Arrow" wasn't as ambitious as it might have been, but it was definitely a lot of fun to see these two costumed heroes butting heads.
The formula when it comes to superhero crossovers is pretty familiar by now. They meet, they bicker, they fight, and eventually they put aside their differences for the greater good. Those were more or less the broad strokes of "Flash vs. Arrow." But at least the script provided a valid reason for these two heroes to fight. And more importantly, it built on the relationship that has already developed between Barry, Ollie, and Felicity these past months.