Some Like It Hot (1959)
Jerry (Jack Lemmon) and Joe (Tony Curtis) are two struggling musicians who witness the St. Valentine's Day Massacre and try to find a way out of the city before they are found and gunned down by mob boss Spats Colombo. The only job that will pay their way is an all-girl band that is fortunately heading to Florida. Desperate, the two dress up as women and hop on the train as Josephine (Curtis) and Daphne (Lemmon). There they meet Sugar (played by Marilyn Monroe), and both men are smitten by her.
In Florida, they run in to more trouble, as Joe finds himself pretending to be a millionaire to get Sugar's attention, and Jerry must fight off Osgood, a rich suitor who is bent on marrying "Daphne." This creates one of the most hilarious moments in cinematic history, when Jerry, after hours of doing the tango with Osgood, returns to tell Joe "I'm engaged." Joe is thrilled, and asks who the lucky lady is. Jerry proclaims, "I am!"
Things get even more complicated, however, when mobster Spats Colombo and his associates arrive at the very same hotel, and Jerry and Joe must scramble to keep their identity hidden from the wise guys and simultaneously keep up the charade with Sugar and the rest of the band.
This movie may not have been the first cross-dressing movie, but it is definitely the pinnacle of the genre. The many clever innuendos and double-entendres that highlight the differences between men and women make this movie a hilarious and classic comedy. There is an even mixture between lowbrow and highbrow comedy, and even some slapstick is thrown in. But the greatest part is Tony Curtis and Jack Lemmon working at least two roles apiece, and playing with the different genders. Just the expression on Curtis and Lemmon's faces as they try to make their way down the train platform in heels...there is an obvious struggle as they walk, but they are both so naturally buoyant that it makes the performance even more incredible.