Fiction writer Christopher Moore has these dogs appear as side characters in his stories set in San Francisco! He's combined them with another SF celebrity vagrant, Emperor Norton (the homeless self-proclaimed emperor of the United States).
In his books, the Emperor travels the streets of San Francisco with Lazarus and Bummer as his brave royal companions, being witnesses or playing some role in the antics of the main characters and the plot. In real life, the Emperor and these two beloved dogs were not traveling companions, but simply shared similar fame and community.