Steve Buscemi, who plays the veteran firefighter Papa, really did serve as a firefighter for a period during his early 20s. In a 2000 "Salon" interview with Stephen Lemons, Buscemi said he was with Engine 55 in Manhattan's Little Italy neighborhood from 1980 to 1984, when he quit to pursue acting full-time. After the terrorist attacks on September 11, 2001, Buscemi (by then a well-known movie star) returned to Engine 55 to help search through the rubble of the World Trade Center looking for survivors or remains. In June 2020, Buscemi told "Entertainment Weekly"'s Derek Lawrence that "The King of Staten Island" was the first time in his acting career that he had ever portrayed a firefighter.
Like Scott Carlin's father in the movie, Pete Davidson's father was a firefighter who died in the line of duty. Scott Davidson's unit, Ladder Company 118 in Brooklyn Heights, responded to the call to the World Trade Center after the terrorist attacks of September 11, 2001. They were rescuing people in the Marriott World Trade Center Hotel when the tower collapsed on the building. Pete was 7 years old. It is specified in the movie that Scott Carlin's father also died in a hotel fire, though not during the 9/11 attacks.
Early in the film, Scott and his friends are watching the horror film The First Purge (2018), which happens to star Marisa Tomei.
The film was scheduled to open in about 100 theaters, mostly drive-ins. Due to the 2020 pandemic, two days before the release date, the theaters were abruptly informed they would not able to show the film. Instead, the release was limited to video-on-demand.