Mutt becomes a character
The previously anonymous sports fan is given a name in the first of his regular strips.
The continuity's initial reason for existence is to report race results: the next day's strip tells us how Mutt's fortunes are faring. This premise eventually disappears, however, and Mutt's character becomes the central subject of the strip.

Harry "Bud" Fisher, "Mr. A. Mutt Starts to Play the Races," cartoon, San Francisco Chronicle 15 Nov. 1907.