When the projectionist is doing an impression of James Stewart in The Spirit of St. Louis (1957), and he points to his landing position in Paris, there's an 8x10 head shot of a woman just to the right and below his hand - it's of "The Girl", Ina Balin.
The marquee of the theatre the projectionist works at lists the film itself as the film that is playing . . . in other words, the film "Now Showing" is the same film.
Dangerfield told Johnny Carson during a guest appearance July 23, 1980 that the film flopped - except in France, where it was a cult hit despite needing subtitles.
Among the many, many stars seen in film clips, movie posters, and photographs are Humphrey Bogart, W.C. Fields, Gary Cooper, Marion Davies, Gloria Swanson, Lillian Gish, Errol Flynn, the Marx Brothers, Stan Laurel, Oliver Hardy, Conrad Veidt, Jimmy Stewart, Greta Garbo, Marlene Dietrich, Charlie Chaplin, Buster Keaton, Ginger Rogers, Fred Astaire, Ruby Keeler, Dick Powell, John Garfield, Peter Lorre, Sydney Greenstreet, and John Wayne.