1914 was Chaplin's first year in films and he starred in 25 movies in just this first year alone. However, many of these films were pretty bad--with practically no plot and just a lot of improvisation that sometimes worked and often didn't. Despite the quality of these films, by 1915 he was probably the #1 star in the world and was lured away from Keystone Studios--with promises of more money and even greater autonomy. Instead of just doing the same old comedies, Chaplin improved upon his "Little Tramp" character and begin carefully scripting his films, and so naturally the quality improved greatly.
ONE A.M. is a great example of his newer and more thought-out scripts for Mutual Studios. While Chaplin is the only person who appears in the film (other than a very brief scene with a cabbie at the beginning), the film is not simply improv or mugging for the camera, but well-choreographed and using complicated props made specially for this film. Several examples would include the spinning taxi meter, the clock with the dangerous swinging pendulum and the amazing and almost intelligent bed.
At first, I thought this whole drunk act theme would become tiresome. After all, at almost 17 minutes, that's a long time to do a drunk "schtick". However, when I thought perhaps Chaplin was milking a scene too much for comedy, he switched to another prop and kept my interest. Funny, well-made and memorable--this is one of Chaplin's best comedy shorts and translates well to viewing in the 21st century.