Suggestions by @dickcooper

Jake T. Austin

as Atom in Nightwing

Colton Haynes

as Anarky in Nightwing

Tom Hardy

as Blockbuster in Nightwing

Amazo

as A.M.A.Z.O in Nightwing

Misha Collins

as Icicle in The Flash

Justin Hartley

as Heatweave in The Flash

Michael Kelly

as Général Wade Eilling in The Flash

Ben McKenzie

as Cobalt blue in The Flash

Teagan Croft

as Raven in The Flash

Ryan Potter

as Beast Boy in The Flash

Jensen Ackles

as Batman in The Flash

Kevin Hart

as Kanja ro in Starfire

Kristen Wiig

as Silver Banshee in Starfire

Donald Glover

as Karras in Starfire

Daniel Kaluuya

as Phy'zzon in Starfire

Diane Keaton

as Martha Kent in Starfire

Kurt Russell

as Jonathan Kent in Starfire

Marlon Wayans

as Johnny Burns in Nightwing

Lauren Tom

as Lillian Worth in Nightwing

Mayko Nguyen

as Adeline Wilson in Nightwing