Rick Blaine (Humphrey Bogart) isn’t taking sides during the early days of World War II. Exiled in the Moroccan city of Casablanca, the gun runner and shady nightclub owner mixes with criminals, refugees and the Vichy French authorities in his Café Américain. Symbolic of American isolationism in the beginning of the war – before the Japanese attack on Pearl Harbour – Rick plays both sides. According to his own admission, he’s a drunkard who doesn’t stick his neck out for nobody.
That changes when his former lover, Isla Lund (Ingrid Bergman) walks into his gin joint with her husband, the famed Czech resistance leader Victor Laszlo. Rick and Isla shared a passionate affair in Paris, just before it fell to the Nazis, when Isla believed that her husband had died in a concentration camp. After learning that he’s still alive, she leaves Rick without explanation to care for him, never seeing Rick again until that fateful day in Casablanca. After their chance encounter, Rick sits alone in the dark, pounding back drinks when his trusty confidant and piano player Sam (Dooley Wilson) enters and tries to convince Rick to get to bed, and that there’s "nothing but trouble" for him there. It’s during this exchange that one of the most memorable lines in movie history was spoken, "Of all the gin joints in all the towns in all the world, she walks into mine."
Rick’s moroseness is accompanied by Sam’s rendition of 'As Time Goes By', the iconic soundtrack to the love story between Rick and Isla, which is used throughout the movie as their relationship is rekindled. But their relationship isn’t the only thing rekindled by Isla’s appearance – Rick's rakish ambivalence is shaken and he’s finally inspired to help the allied war effort. Bogart delivers the line with a focus on the “walks into” section, the dialogue denoting how that simple action of Isla appearing is enough to uproot Rick’s life and help him rediscover his purpose.
Casablanca (1942) is routinely listed as one of the best films of all time. On the DVD commentary, critic Roger Ebert comments that Casablanca is "probably on more lists of the greatest films of all time than any other single title, including Citizen Kane", which is certainly saying something. The film’s enduring popularity is due to the remarkable performances from Bogart and Bergman, its release just after America entered WWII, ear-worm soundtrack, iconic lines and as an exemplar of Golden Hollywood cinema. Keeping it freshly in pop-culture consciousness are endless parodies, homages and tributes, which feature the "walks into" line in many. Seasame Street have done a kid-friendly version, it’s been remade and remixed as a Tarantino-style parody, featured in Ocean's Eleven, parodied in The Simpsons, remade as LEGO, had a song named after it, and appeared on AFI's 100 Years...100 Movie Quotes list.
– Matt Millikan