1) Harley Quinn’s Origin Story
There’s been a fair bit of controversy about this over the past week, but following The New 52 comics by having The Joker be the one responsible for creating Harley Quinn feels right to me.
Originally, Arkham Asylum psychiatrist Dr. Harleen Quinzel fell in love with The Joker and decided to become his sidekick, but both this and the Comic-Con preview make it clear that the big screen version is going to be forcibly changed into Harley.
That just means her backstory is all the more tragic and disturbing, and makes the Clown Prince of Crime an even more despicable figure. The sight of him basically baptising her in the same A.C.E. Chemicals vat he became The Joker in feels like a soon to be iconic moment, and it will be very interesting to see how this all plays out when Suicide Squad finally hits theatres.