The Floorwalker was Charlie Chaplin‘s first Mutual Film Corporation film, made in 1916. The film stars Charlie Chaplin as the Little Tramp, as a customer who creates chaos in a department store. He inadvertently becomes entangled in the scheme of the store manager, played by Eric Campbell. Along with the store’s floorwalker, played by Lloyd Bacon, they scheme to embezzle money from the store. Edna Purviance plays a minor role as a secretary to store manager.
The film is famous for the first “running staircase” used in films. It is used for a series of slapstick that climaxes with a frantic chase down an upward escalator and finding they are remaining in the same position on the steps no matter how fast they move.
In the film, Charlie and the store’s floorwalker stumble into opposite doors of an office and are intrigued by their likeness to each other. They mirror each other’s movements to deft comic effect in a “mirror scene”.
This scene has been duplicated many times, most famously in the Marx Brothers film Duck Soup. Later renditions can be found in the Bugs Bunny cartoon Hare Tonic, the Mickey Mouse cartoon Lonesome Ghosts, and in the TV series The X-Files. A scene in The Pink Panther, with David Niven and Robert Wagner wearing identical gorilla costumes, mimics the mirror scene. Harpo Marx did a reprise of this scene, dressed in his usual costume, with Lucille Ball also donning the fright wig and trench coat, in an episode of I Love Lucy titled Harpo Marx. Additionally, an early episode of The Patty Duke Show contains a mirror scene in which the characters Patty and Cathy Lane (both played by Patty Duke) act out the mirror scene.
(thanks to Wikipedia)