Special Guest Stars Melissa Benoist as Supergirl / Kara Zor-El / Kara Danvers David Harewood as Hank Henshaw / J'onn J'onzz / Martian Manhunter John Barrowman as Cutter Moran Victor Garber as Digsy Foss' Husband Chris Wood as Mon-El Chris Wood as Tommy Moran Jeremy Jordan as Grady Guest Stars Michelle Harrison as Nora Allen Darren Criss as Music Meister Co Starring Liam Hughes as Young Barry Allen Braden Chase as Goon #1 Gili Roskies as Patron Uncredited Candice Patton as Millie Foss Carlos Valdés as Pablo Jesse L. Martin as Digsy Foss