The two biggest former stars are obviously The Flash’s Grant Gustin and Supergirl’s Melissa Benoist, and we saw Blake Jenner, who was then Benoist’s husband, get involved as Supergirl’s Adam Foster.
As stated earlier, Adler is actually the fifth Glee actor to appear in the Arrow-verse.
Is anyone shocked that we’re seeing another Glee veteran getting a music-oriented role?
Darren Criss actually gave the show its biggest musical showstoppers yet as the quasi-villainous Music Meister, so we’ll see if Jaco Birch has more to add there.