While shooting one of the fire scenes for the movie, a special effect fire got out of control and burned the whole set down, including the studio stage, into which it was built, and almost all of the crew's equipment. Nobody was seriously injured, and filming resumed the next day, with equipment being hauled in from all over the world.
With one exception, all of the shots with Renée Zellweger being close to and around fire were real (practical effects). The one CG-enhanced shot is the wide angle of her sitting passively on the couch while the room was burning around her. This was shot twice: once with her and no fire, and once with fire and no Zellweger.
Christian Alvart: [mirror shot] As Doug (Bradley Cooper) pulls hornets out of his right ear with a cotton swab, Doug is reflected by three mirrors, effectively showing him four times from all angles (and the hornets as well).
In a couple of scenes, Lilith is seen wearing or holding items of red. In Doug's funeral scene, her collar is red, and as she gets off the bus, her umbrella is red. Red is seen as the color of the Devil.