The Flash Supergirl Musical Crossover: 14 Easter Eggs & References In 'Duet' You Need To See
12. Glee Reunion
A Glee reunion has already played out numerous times in the Arrowverse, thanks to alums Gustin and Benoist appearing in two of the leading roles.
This time, however, the reunion was even bigger (and better) with Darren Criss cast in the role of the Music Meister. He played Blaine Anderson, who first appeared in Season 2 as the leader of The Warblers, and begins a relationship with Kurt (which would prove to be that series' best). Criss had a lot of charisma there, and it's on display again here.
On Glee, when Blaine leaves the Warblers, he's replaced as their leader by Sebastian Smythe - played by none other than Gustin himself, with the pair acting together fairly frequently, although in that case Gustin is the one seen more as the villain.
Similarly, when Benoist's Marley Rose arrives in Season 4 as a main cast member, she's involved heavily alongside Criss' Blaine, making this a true reunion for everyone (although Gustin and Benoist never exchanged any dialogue on the show).