In the two photos above, a chihuahua is pulling wagon with a teddy bear at the Pecan Festival Street Festival in Austin, Texas. Photos are by Ken Cobb, who has an extensive Flickr photostream under the name "killercorn."
killercorn's photostream

The chihuahua pulling the teddy-wagon is named Gidget and she belongs to Noel Kalmus of Abilene. By the name "saeglopur" Noel too has a Flickr photostream with drawings and photographs, as well other photos of Gidget and other dogs in the collection, including a "puppycab" of the teddy-wagon in action, and this lovely photo of Gidget, below, peaking through a hole in a fence.
saeglopur's photostream