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 Jeremy Jordan as Grady John Barrowman as Cutter Moran Chris Wood as Mon-El Chris Wood as Tommy Moran 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 Jesse L. Martin as Digsy Foss Carlos Valdés as Pablo