WARNING: The following contains spoilers for Batman: The Long Halloween, Part 1, now available digitally and on Blu-ray and DVD.
In Batman: The Long Halloween Part 1, it's no surprise that changes were made to the source material. The 13-issue series from Jeph Loeb and Tim Sale packed a lot in, and even with the film split into two parts, adjustments had to be crafted to tell a more cohesive story. With that said, let's break down how this animated adaptation differentiates from its source material.
Harvey Dent's Plan in The Long Halloween
In the comic, Harvey was assaulted by Carmine Falcone's men as an intimidation move. This act riled him up so much that he'd fake his own death after an Irish gang bombed him on behalf of the mob, placing his wife in the hospital. He'd then go undercover as the leader, Mickey, using a mask Batman made, hinting at the Two-Face to come.
Part 1 doesn't have the parking lot beatdown or Harvey faking his death. He's also the one hospitalized in the movie, not Gilda, and takes a gun to exact revenge on the gangsters, only for Jim Gordon to calm him down. Harvey, Batman and Catwoman also flip a coin to decide whether to burn Falcone's money, with the Dark Knight giving Harvey the coin he'd later use to become Two-Face. However, in the comic, Catwoman wasn't in the scene, nor was the coin.
Family Dynamics in The Long Halloween
The Gordons spend a lot of time with the Dents in the books, mostly because Jim can tell Harvey's starting to break bad. Barbara also wants to help Harvey's wife, Gilda, get over the trauma of being a constant target. Part 1, on the other hand, makes Harvey a neglectful husband and has Gilda on her own, drinking by herself.
This animated movie also makes Jim's daughter Barbara older, foreshadowing the Batgirl to come, while she was just mentioned by name in the comic. As for Alfred and Bruce, the source material shaped them as an experienced team, but the film has Alfred being more of a lecturer and father to a bumbling Caped Crusader, who is consistently making mistakes.
The Villains' Motivations in The Long Halloween
In Part 1, Catwoman knows Bruce is Batman, which is why she helps out so much, even going as far as to go on the train heist to force him into a date. She also has a much larger disdain for Falcone in the movie, which is something that's only briefly touched upon in Loeb and Sale's story.
As for the Joker, Part 1 has him breaking out of Arkham to go after the Holiday killer because he's jealous Batman's giving a new villain attention. In the book, however, Joker's already on the outside and starts his own investigations. Part 1 also changes the Irish gang to members of the Triad, and when the Dark Knight traps their leader Mickey under the sewers, he doesn't fight Solomon Grundy.
The Long Halloween's Dark Assassinations
In the film, a more conflicted, bitter Alberto is bullied by Carmine, his dad, and when Batman and Selina confront him on the party yacht, someone shoots Alberto and he falls into the propellers. Batman chases after the killer, who escapes via boat, leaving Bruce stranded on the ship without a prime suspect. The books didn't include any of this, and Alberto actually hated seeing Bruce snooping around his dad and was more loyal to the clan in the source material.
Alberto's death in the comic saw him shot on the yacht, but with only Falcone's sister, Carla, nearby. Carla's tapped as a suspect heavily in the book, too, but Part 1 keeps her in the background to focus more on Batman and Selina. The film also leaves out the assassination of banker Richard Daniel, who Batman pressured into not working for Falcone.
Bruce Wayne's Brainwashing in The Long Halloween
The post-credits scene of Part 1 sees Falcone using Poison Ivy to infect and brainwash Bruce at Alberto's funeral so his business operations can keep going. Her vines wrap around Bruce's hand during a handshake and start corrupting his mind, but this moment plays out differently in the comic. In Loeb and Sale's story, when Ivy pretends to be a rose vendor, selling a flower while Bruce and Selina are out on Valentine's Day, one of the thorns pricks Bruce and the corruption takes over when he returns to the mansion.
To see all of the changes made from the comics, Batman: The Long Halloween, Part 1 is available digitally and on Blu-ray and DVD.