I was thinking about how the multiple earths could represent different retro DC screen versions. I am aware we will be lucky to get even half of it, as the Arrowverse has their own characters they’ll want to showcase:
BATMAN 66: Burt Ward and Julie Newmar are still with us, maybe they could cameo as elderly Dick Grayson and Selina Kyle morning their Batman’s loss?
WONDER WOMAN 77: Lynda Carter has already appeared in Supergirl as Olivia Marsdin
DONNER’S SUPERMAN: Marc McClure cameoed in Justice League and Helen Slater Is Supergirl’s adoptive mom in that series.
SUPERBOY: According to imdb John Haymes Newton seems to be more active as an actor than Gerard Christopher
BURTON/SCHUMACHER’S BATMAN: A long shot - Michael Keaton’s film career seems to be in the rise again, Chris O’Donnell is on NBC, the rest are either too big stars or retired (Jack Nicholson)
THE FLASH OF EARTH-90: Established in Elseworlds, John Wesley Shipp returned as an alternate Barry, he could return? Amanda Pays, Alex Desert, Vito D’Ambrosio and Mark Hamill have all played Earth-1 characters of their 1990 characters. Someone suggested Hamill could play his Joker in live action which would be super cool!
LOIS & CLARK: Dean Cain and Teri Hatcher have both completely different characters on Supergirl. They have both expressed interest in doing a ’25 years later’ Lois & Clark thing but WB/DC are obviously doing different things with Superman. An appearance as their original roles on COIE would be nice
SMALLVILLE: Erica Durance and Laura Vandervoort have different roles on Supergirl. Stephen Amell made social media go crazy when he posted a picture with Tom Welling and Michael Rosenbaum, but that turned out to be a meeting for his wine company. How cool would it be if they could finally get Welling in a Super suit? Also Alexander Luthor was a major player in the original Crisis comic book.
BIRDS OF PREY – An obscure one, about Oracle, Huntress and Black Canary protecting ‘New Gotham’ from crime. Batman disappeared after Catwoman’s death at the hands of the Joker, voiced by Mark Hamill.
THE DARK KNIGHT LEGACY: Aren’t all the stars too big for a CW show?
SUPERMAN RETURNS: Brandon Routh is of course The Atom on Legends of Tomrrow, a well established character. I doubt they’d able to get any other main actors back.
OTHERS: Gotham ends this year and the DC Universe streaming service is already building its own universe of shows. To get more obscure, there were also Swamp Thing and Human Target shows. Also a Superman allegedly built for Tim Burton’s Superman Lives (but worn for the 2003 FlyBy screen tests by Henry Cavill and Brandon Routh) was taken out of the archives for a recent DC Daily. It’d be cool to establish it on screen here, it’s well-known in fan circles from leaked photographs.