You actually met the town clerk Dewy Cheatum. The Mayor is older, shorter, and not nearly as fat (the mayor is in the pic posted above). The Mayor has a slight southern accent, and his name is Christopher George Weaver.
Other citizens of Main St. include Scoop Sanderson (reporter for the Main St. Gazette), Constance Purchase, Noah Lott, Shiela Shufflehop, and Ms. Hildegarde Olivia Harding (sufferagette running for Mayor even though women don't yet have the right to vote or hold office). There is also a fire chief, but I don't recall his name off the top of my head, and I've forgotten a few other ladies.
There are also atmosphere performers in Adventureland and Frontierland from time to time, like Gold Dust Gus, the prospector.
In the past there have been similar characters in Harambe and Dinoland at DAK and at Innoventions in Epcot. Of course, Streetmosphere at the Disney-MGM Studios is the oldest and largest location for atmosphere performers. All of those areas, as well as Dinner shows and speaking/singing roles in stage shows are staffed by the same Equity performers department. Constance Purchase is also Rose Petal (of Perfectly Princess Tea) and a sub at Hoop Dee Doo. Scoop also performs the roll of Grand Duke in Cinderellabration, Noah Lott is Merlin, and Dewy Cheatum can be found many nights in many roles at the Adventurers' Club on PI.
When parades are taped at WDW, many of these performers get to be "Warm-up" announcers for the crowds of extras.