A great deal of backstory for Harvey Dent, including his parents, Harry and Lucy, and how Harvey came to meet Rachel.
The Joker, while posing as Bozo before his robbery of Gotham National Bank, stood on the sidewalk waiting for his men to pick him up. An elderly woman stood near him and he slipped her a hundred dollar bill, either to walk away or keep silent about seeing him there.
The Chechen had a lackey named Burton who told him about Scarecrow, and set up the meeting for them.
Scarecrow sold his drug to a junkie for little money, then after he took the drug was killed by Scarecrow, with the intention of learning its effects.
Joker Venom is utilized in the novel, on a private detective that Sal Maroni hires to find information on the Joker.
Apparently originally a knife held the note to Brian Douglas' chest, but an alternate scene was filmed showing the note held by a pin.
Following the charity event in Bruce's penthouse, the following scene takes place: The Joker looked back toward the penthouse as his getaway car sped away. He breathed hard, exhilarated even as a stream of blood ran down his face and tells the driver how the Batman saved Rachel and starts to wonder if they have a relationship or Batman does this with everyone and this can lead to his downfall. He smacked the back of the driver's seat. Driver: "What do we do about Dent?" The Joker: "I'm a man of my word."
Instead of saying he's going after Rachel, Batman said "Dent knew the risks."
Rachel's last words before dying: "Bruce. Harvey. I love you."
Gordon made it clear that the Joker switched the locations of Rachel and Harvey in his directions and cries.