| "Worlds Finest" | |
|---|---|
| Supergirl episode | |
 A promotional poster for the episode, inspired by the cover of Superman #199 (1967) | |
| Episode no. | Season 1 Episode 18 |
| Directed by | Nick Gomez |
| Story by | Greg Berlanti |
| Teleplay by |
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| Production code | 4X7618 |
| Original air date | March 28, 2016 |
| Guest appearances | |
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"Worlds Finest" is the eighteenth episode of the first season of the American superhero television series Supergirl. It aired on CBS on March 28, 2016. The episode's teleplay was written by Andrew Kreisberg and Michael Grassi, and directed by Nick Gomez.
The episode features a crossover appearance by the title character of the CW series The Flash (also developed and produced by Greg Berlanti and Kreisberg), marking the first episode of the series to feature a character from the Arrowverse, and the first character from a CW series to cross over to a CBS series before the show itself moved to the CW network. The episode loosely intersects with the events of The Flash season 2 episode "Versus Zoom".
The episode reunites Melissa Benoist with her former Glee recurring co-star Grant Gustin, who portrays the Flash. The episode title was inspired by the World's Finest Comics series, in which Superman would team up with various other DC superheroes, including the Flash.