Ninety-nine percent of romance stories in American cinema focus on couples meeting, hooking up, and living happily ever after, sometimes marrying just before the credits roll. Nick and Nora Charles (William Powell and Myrna Loy) were a rare example of a couple that was already married; they knew each other well, bickered, laughed, teased each other, put up with one another, and seemed to enjoy each other's company. They even kissed from time to time, though they slept in separate beds and, when they had kids, it took Nick completely by surprise. They were hardly a realistic couple, but they must have provided comfort and hope for thousands of real-life couples during the Depression and WWII.
Powell and Loy first teamed up in The Thin Man (1934), a wonderful, unique movie that benefits from a glossy MGM production design and director W.S. Van Dyke's fast, loose shooting style; it effortlessly combined of comedy, murder, and romance. Nick and Nora's routine consisted of Nick trying not to do any more detective work and instead enjoy his wife's money (and the liquor it buys), and Nora trying to push her husband into solving the latest disappearance or murder case. Five more Thin Man movies followed from 1936 to 1947, even though the actual "thin man" referred to a suspect in the first movie (and not to Nick).
Powell and Loy also made eight additional movies together, including the Best Picture Oscar winner, The Great Ziegfeld (1936). Their chemistry was unmatchable, and has yet to be equaled; not even Fred Astaire and Ginger Rogers could sustain their magic for so long, and over so many pictures. Powell and Loy were so essential to each other that when one appeared without the other something seemed to be missing. It's perhaps due to this bond that they could actually get away with playing a married couple, rather than a meet-cute couple that gets married in the end; it was as if they were "meeting cute" every step of the way.
The above clip is from After the Thin Man (1936), the second movie in the series.