Stage Door Canteen (1943) is a musical film featuring many cameo appearances by celebrities. From one poster I saw, apparently there are 62! The majority of the film is a filmed concert, although there is some storyline thrown in for good measure. But let's just say you're not really watching it for the plot.
This WWII film celebrates the work of the "Stage Door Canteen", which was actually a real phenomenon created in New York City as a place for both American and Allied servicemen on leave to socialise with and be entertained or served by theatrical celebrities.
The real Stage Door Canteen on 44th Street could not be used for the filming as it was too busy receiving real servicemen, which is kind of neat when you think about it.
Until next time :)