!!The 1987 movie
* ActorInspiredElement: It was Creator/SeanConnery's idea to film the "blood oath" scene between Ness and Malone in a Catholic church. Originally it was going to take place on the street (in the same scene that follows the church scene). Connery felt that a church would be the only "safe" place in Chicago where the two characters would make such a commitment to fight Capone.
* CaliforniaDoubling: The Canadian Border raid was film at Hardin, Montana, which is about as far away from the Canadian border as you can get while still be in Montana.
* DyeingForYourArt: Creator/RobertDeNiro gained 30 pounds for his role as Capone, and (allegedly) even insisted on wearing the same clothes Capone did, right down to his silk underwear.
* FakeNationality: Edinburgh-born Creator/SeanConnery as an Irishman, Havana-born Creator/AndyGarcia as an Italian-American (first generation), and the Kansas-born Native American and Romany Billy Drago as an Italian.
* StarMakingRole: For Creator/KevinCostner and Creator/AndyGarcia.
* ThrowItIn: Creator/KevinCostner ad-libbed the line "He's in the car," after [[spoiler:throwing Nitti off of the roof]].
** Creator/HarrisonFord turned down the role of Eliot Ness. Creator/MelGibson turned it down in order to star in ''Film/LethalWeapon''. Creator/MickeyRourke, Creator/MichaelDouglas, Creator/JeffBridges, Creator/NickNolte, Creator/JackNicholson, Creator/WilliamHurt, Creator/TomBerenger and Creator/DonJohnson also passed on it.
** Suffolk-born Creator/BobHoskins was cast as Al Capone, but was paid a bundle of money once Creator/BrianDePalma brought Creator/RobertDeNiro, the director's first choice all along, onboard.
** Creator/GeneHackman was offered the role of Malone.
** In the original script, the final gunfight had Eliot Ness and George Stone battling Capone gunmen on a stopped train. Creator/BrianDePalma conceived the gunfight on the steps in Chicago's Union Station when Paramount decided that staging the scene and finding a 1930s period train would be too expensive.
** There was originally a different ending for the movie. It was to have been a scene with the camera shooting a close up of Capone's face as it is being warmed up for a shave. And then the camera would have craned up to show the audience that he has reporters around him, but he is in his jail cell.