The storyline of the film follows several women who volunteer for the Canteen and who must adhere to strict rules of conduct, the most important of which is that while their job is to provide friendly companionship to and be dance partners for the (often nervous) men who are soon to be sent into combat, no romantic fraternization is allowed. One volunteer who confesses to only becoming involved in the Canteen in order to be discovered by one of the Hollywood stars in attendance, ultimately finds herself falling in love with one of the soldiers.
The real Stage Door Canteen on 44th Street could not be used for the filming as it was too busy receiving real servicemen. It was recreated in New York and at the RKO Radio Pictures studio in Culver City. There also was a Stage Door Canteen in the Academy of Music Building in Philadelphia.
Star appearances range from momentary cameos, such as Johnny Weissmuller, seen working in the canteen's kitchen, to more substantial roles such as Katharine Hepburn. There really isn't a much of a plot, but it's a lovely showcase of the wartime popular music, comedy skits and stars. Try to identify as many stars as you can, then head over to the WikiPedia link where there is the complete list.