The Flash Supergirl Musical Crossover: 14 Easter Eggs & References In 'Duet' You Need To See
9. West Side Story
Another musical to get a lot of references in this episode is West Side Story, from which a fair bit of the overall plot is borrowed.
This is where the episode gets the star-crossed love story between the new versions of Iris and Mon-El, and subsequently the fathers deciding to go to war with each other despite giving the relationship their blessing. And, again, it gets directly referenced, with Barry saying "It's just like West Side Story."
In response to that, Kara references another musical, saying "I was thinking more like The Fantasticks." Again, that was a musical that featured star-crossed lovers, sort of. Rather than actual warring factions, it sees two neighbouring fathers pretend to feud in order to trick their children into fall in love with each other. Yeah, this is definitely more West Side Story.
Sticking with the 60s theme (well, the WSS film came out in the 60s anyway, even if the musical was earlier), Benoist opens the singing with a rendition of Moon River, from the song Breakfast at Tiffany's, and is later referred to as Audrey Hepburn, the star of that movie.