The internet is all a’buzz about this one — for a variety of reasons, but the big one being the Big Bad — the reveal of Ra’s al Ghul in season 3.
Ra’s al Ghul is perhaps best known to the viewing public as the enemy in Christopher Nolan’s Batman Begins. His origins go back to a classic run on Batman in the early ’70s, and was created by one of the most acclaimed Batman teams ever, Denny O’Neil and Neal Adams.
He was name-dropped several times in Arrow’‘s season 2.
Stephen Amell had him a time at Comic-Con, and showed some team spirit by wearing a Flash baseball hat:
Final note of the trailer — I can only assume that, in the end, Ra’s al Ghul doesn’t end up being an out-of-work actor/stooge. I’m looking at you, Mandarin.