Suggestions by @robertwaynecarroll

Billy Crudup

as Henry Allen in The Flash

Jesse L. Martin

as Joseph West in The Flash

Kiersey Clemons

as Iris West in The Flash

Monica Dolan

as Mrs. Stephen (Erika Stephen) in Hit-Girl

Steven Mackintosh

as Mr Stephen (Carmelo Stephen) (Cameo) in Hit-Girl

Clark Duke

as Uncle Marty/Battle Guy) (Marty Eisenberg) (Gets killed by assassins) in Hit-Girl

Evan Peters

as Uncle Todd (Todd Haynes) (Returns as Ass-Kicker Mid-Credits Scene) in Hit-Girl

Joey King

as Tina Lloyd (Jamie's Sister) (Cameo) (Flashbacks) in Hit-Girl

Ross Lynch

as Tyson Brown Macready (Police Sergea3nt) in Hit-Girl

Ross Lynch

as Tyson Brown Macready (Police Sergeant) in Hit-Girl

Eisenhower Jr (Bella)

as Eisenhower Jr (Bella) in Hit-Girl

Laura Bailey

as Supergirl (Kara Zor-El) (Cameo) (Injusticeverse) in The Flash

Alan Tudyk

as Green Arrow (Oliver Queen) (Cameo) (Injusticeverse) in The Flash

Vanessa Marshall

as Black Canary (Dinah Lance) (Cameo) (Injusticeverse) in The Flash

Caity Lotz

as White Canary (Sara Lance) (Cameo) (Arrowverse) in The Flash

Grant Gustin

as Savitar in The Flash

Tom Holland

as Flash III in The Flash

Gillian Jacobs

as Harley Quinn (Harleen Quinzel) (Cameo) (Injusticeverse) in The Flash

Kevin Conroy

as Batman (Bruce Wayne) (Cameo) (Injusticeverse) in The Flash

James Norton

as Green Lantern (Guy Gardner) (Cameo) (Campbellverse) in The Flash