- Killer Frost and Vibe
- the existence of the multiverse, with the introduction of Earth 2 into the mythos
- Jay Garrick (the Earth 2 Flash)
- Atom Smasher
- Hawkman and Hawkgirl
Season 1 drew unashamedly from the comic book, using the vast majority of the core rogues gallery with a few notable exceptions – Mirror Master, Dr Alchemy/Mr Element and Abra Kadabra – will any or all of these make an appearance?
- Ray Palmer is believed to be dead, and Starling City has been renamed “Star City” in his honour.
- Diggle gets a costume (though the helmet has received some criticism for being too derivative of Magneto)
- Constantine appears, presumably to assist with the repercussions of Sara’s Lazarus Pit resurrection.
- Mr Terrific and T-spheres
- Lonnie Machin (Anarchy)
Legends of Tomorrow
- Vandal Savage is the big bad, with Rip Hunter’s team battling him across time
- Hawkman is 5000 years old, a reincarnation dating back to Egyptian times
- Hawkgirl is said to have one of the more faithful origins to the comics, though which origin remains to be seen
- Valentina Vostok – will she become Negative Woman and lead to the appearance of others from the Doom Patrol?
- Vartox – whilst somewhat removed from the Zardoz-inspired tragi-hero from the 70s Superman comics, his arrival does open a door to future alien characters in the show
- Red Tornado
- The Batcave and the clues it holds to secrets from Thomas Wayne’s past
- Mr Freeze
- Clayface – of the three versions to choose from, Basil Karlo would seem the most likely candidate given his lack of powers in the original comics
- Mad Hatter
- The Court of Owls – as a shadowy elite behind much of Gotham’s past, it’s not impossible to see them as stepping in as the crime families start to lose their hold on the city