Most of Chaplin's very earliest shorts for Keystone and Essanay look fairly primitive now as if they were paving the way for the Mutual series in which his comedic art reached its first peak. Some critics have even preferred the comic spontaneity of the Mutuals to the more serious concerns of the later more mature films. The Immigrant (1917) a touching romantic comedy hints at the Chaplin features with its bittersweet tone, in contrast One A.M. (1916) is a wonderfully funny solo performance in which a drunk tries to enter his house then his bedroom. Chaplin was also a drunk in The Cure (1917) while Easy Street (1917) was the first film to really recall Chaplin's poverty stricken youth with the T shaped set he liked to use. The First Nationals have often been neglected in favour of the Mutuals but they are a less consistent  but can be a more rewarding series of films. In A Dog's Life (1918) Charlie adopts a thoroughbred mongrel Scraps, in Shoulder Arms (1918)  he dreams of capturing the Kaiser. The most underrated of the films to me is The Idle Class (1921) in which Chaplin plays a dual role of the Tramp and an alcoholic millionaire.
  

DVD available from Image Entertainment for the Mutuals :
http://www.amazon.com/

from Warner Home Video for the First Nationals :
http://www.amazon.com/