For It: Chapter One, see here.
- Ability over Appearance: Bill Hader doesn't look especially like Finn Wolfhard, but he was many people's (including Wolfhard himself) top choice for the role, so no one really cares.
- Acting for Two: Molly Atkinson plays both the reprised role of Eddie's mother and the new role of his wife. Also, Katie Lunman plays one of Pennywise's victims, Betty Ripsom, in the first film (and voices her in the second), and plays the male character Chris Unwin (who, in the book, is supposed to be the youngest of Webby's gang at 15) in the second film.
- All-Star Cast: The cast for the Japanese dub is comprised of well-known Anime voice actors, including Yoshimasa Hosoya (Bill), Ayahi Takagaki (Bev), Daisuke Ono (Ben), Hiroshi Kamiya (Eddie), Jun'ichi Suwabe (Richie), along others.
- Approval of God: Stephen King has described Richie being in love with Eddie as a "kind of genius"
addition to the story. - Ascended Fancast: In the aftermath of It (2017), Jessica Chastain and Bill Hader were popular fancasts for Adult Bev and Adult Richie, respectively, with even the younger actors agreeing. Chastain and Hader were cast in the end.
- The Cast Showoff:
- One of Richie Tozier's character traits is his ability to do "voices" and impressions. Bill Hader is a well-known impressionist, famous for the celebrity impressions he did for years on Saturday Night Live. With this in mind, screenwriter Gary Dauberman wrote a scene in which Richie does an impression of Al Pacino, a voice that Hader is quite good at. However, Hader requested that the impression be removed from the script because the Pacino impression was old material and he didn't feel like doing it again. In the finished film, Bill Hader deploys his skills doing a solid impersonation of Bill Skarsgard's Pennywise.
- Bill Hader asked Bill Skarsgard about his "eye trick". Again Skarsgard showed that this wasn't CGI and scared the pants off of Hader.
- Crosscast Role: Katie Lunman as Chris Unwin.
- Darkhorse Casting:
- While James McAvoy, Jessica Chastain, and Bill Hader are all certainly established Hollywood stars, the other main cast members are much less well known. James Ransone is best known for his work in The Wire and Sinister. Andy Bean and Jay Ryan are both best known for their television work as Greg in Power and Vincent in Beauty and the Beast (2012), respectively (though Ryan also has/had significant roles in other TV shows). In fact, It: Chapter Two will be both Ransone's and Ryan's first time as leading men in a major theatrical film. Likewise, Isaiah Mustafa is most famed for being The Man Your Man Could Smell Like, which is a viral commercial, and, to a lesser extent, his role in the show Shadowhunters.
- Likewise, the supporting cast aren't the major Hollywood stars many fans were expecting the sequel to such a smash hit to get. It's mostly people who have acting experience from lesser known films and TV shows, such as Jess Weixler, who’s mainly known for her lead role in the independent horror movie Teeth.
- Dawson Casting: Jake Weary (28) as Webby, the leader of the gang of homophobic teenagers who attacked the gay couple Adrian Mellon and Don Hagarty.
- Dueling Works: The film was released just under a month after Scary Stories to Tell in the Dark (2019), a movie with a similar theme of small-town friends facing supernatural murders. Chapter Two has been more successful at the box office, though critical reception to Scary Stories has been more favorable.
- Fake American:
- Scottish James McAvoy as Bill Denbrough.
- Kiwi Jay Ryan as Ben Hanscom.
- Canadian Finn Wolfhard reprising his role as child Richie Tozier.
- Australian Nicholas Hamilton as Henry Bowers.
- Hide Your Pregnancy: Jess Weixler (Audra) was pregnant during filming.
- Hostility on the Set: More awkwardness than hostility. Andy Bean (Adult Stanley) said that it was awkward working with the Innocently Insensitive Wyatt Oleff (Young Stanley). He was annoyed with Oleff trying to give him notes on how to play Stanley, and he also stated that he felt a little offended how Oleff stated that he'd wanted Joseph Gordon-Levitt to play Stanley as an adult. Otherwise, Bean still tried to remain patient with Oleff throughout the production.
- Hypothetical Casting: The members of the Loser's Club were asked whom they wanted to play their adult parts: Finn Wolfhard (Richie Tozier) said Bill Hader, Sophia Lillis (Beverly Marsh) said Jessica Chastain, Chosen Jacobs (Mike Hanlon) said Chadwick Boseman, Jack Dylan Grazer (Eddie Kaspbrak) said Jake Gyllenhaal, Wyatt Oleff (Stanley Uris) said Joseph Gordon-Levitt, Jeremy Ray Taylor (Ben Hanscom) said Chris Pratt and Jaeden Lieberher (Bill Denbrough) said Christian Bale. Wolfhard and Lillis' choices were the only two that ended up being cast, likely for budget reasons.
- Irony as She Is Cast: Here, Nicholas Hamilton plays a violent homophobic bully. But in real life Hamilton is part of the LGBTQ+ community, and is a staunch progressive and LGBTQ+ ally.
- The Original Darrin: Arturo Mercado Jr. and Víctor Ugarte, who voiced the younger Richie and Eddie, respectively, in the Latin American Spanish dub of the original 90's miniseries, came back to voice their adult versions.
- Production Posse: Jessica Chastain and Megan Charpentier previously worked with Andy in Mama.
- Queer Character, Queer Actor: Xavier Dolan and Taylor Frey are gay just like their characters, Adrian Mellon and Don Hagarty.
- Refitted for Sequel:
- The sequence adapted from the novel involving the kids building an underground clubhouse in the Barrens, in which they participate in a "Smoke Hole Ceremony," learning about IT's first arrive on earth and how it ended up in Derry in the form of an asteroid was shot for the first film. Budget and time constraints prevented this. The scene instead features in one of the Losers' flashbacks to when they were kids.
- The scene where the Losers learn of IT's time in Old Derry, and the killing spree that occurred, with a flashback to the 1600s before It took the form of Pennywise was actually fully shot but left on the cutting room floor of the first film. While it wasn't included in the sequel, Bill's vision after being drugged by Mike shows IT terrorizing the local indigenous people until they escaped the monster's sphere of influence.
- The scene where Stan walks out during his bar mitzvah, while Richie claps excitedly for him was a cut scene from the first movie, appearing in the special features on DVD, before being added to the sequel.
- Separated-at-Birth Casting: All of the adult actors bear more than a passing resemblance to their younger counterparts. Especially James Ransone and Jack Dylan Grazer (Eddie) and Andy Bean and Wyatt Oleff (Stan).
- What Could Have Been:
- Idris Elba expressed interest in playing Mike (which would have reunited with his Prom Night (2008) co-star James Ransone, who is cast as Eddie) prior to Isaiah Mustafa's casting.
- Seth Green, who played the young Richie in the miniseries, expressed interest in playing the adult Richie.
- At one point, the destruction of the Black Spot night club, which was planned to feature in the first movie, was to be refitted as the opening scene of Chapter Two.
- After the character was Adapted Out of the first film, Director Andy Muschetti stated that Maturin the Turtle would make a physical appearance in Chapter Two, but the scenes including him were ultimately cut.
- Another scene that was Adapted Out of the first movie and meant to be refitted for the sequel was a scene showing Pennywise interacting with the settlers of Derry and blackmailing a mother to surrender her infant in exchange for her life, with a still of a deleted scene showing IT assuming a humanoid form with crimson skin.
- Muschetti also stated that a flashback in the thrift shop was planned, in which a younger version of the shopkeeper (played in modern day by Stephen King), would have appeared, played by King's real-life son Joe Hill. The scene was ultimately scrapped due to "serving no dramatic purpose."
- The World of IT artbook reveals all sorts of concept art for IT — particularly its final form — that went unused.
- Multiple versions of Eddie's death scene were filmed, including some that were longer and more emotional.
- Guillermo del Toro was approached for a cameo as a janitor but turned it down due to scheduling problems.
- Mike Hanlon was supposed to have a subplot in which he was suffering from drug addiction, but it was written out, most likely because it took away from the story.
