Special Guest Stars Melissa Benoist as Supergirl / Kara Zor-El / Kara Danvers David Harewood as Hank Henshaw / J'onn J'onzz / Martian Manhunter Victor Garber as Digsy Foss' Husband John Barrowman as Cutter Moran 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 Jesse L. Martin as Digsy Foss Candice Patton as Millie Foss Carlos Valdés as Pablo