At a boarding house, Florence Lawrence is trimming a hat while a couple of the male tenants clumsily try to flirt with her. They are stopped by Stuart Blackton Jr, who peppers them with pellets. When Miss Lawrence leaves, he takes the bust she uses to model her hats and places it in the common bath tub; the men think this is Miss Lawrence taking a bath and are heartily embarrassed.
The practical joke as the totality of a film comedy began with the Lumiere's L'ARROSEUR S'ARROSE, and continued in that form through about 1912. It took some time before the film makers would ornament the basic gag, or extend the movie to show consequences in a primitive story. Although there were more sophisticated comedies by this time this came out, it was still an ongoing form.