A brag is a creature from the folklore of Northumberland and Durham that usually takes the form of a horse or donkey. It is fond of tricking unwary wayfarers into riding on its back before throwing the rider into a pool of water or bush, afterward running off laughing, much like the Bäckahästen (brook horse) or kelpie. The brag is also said to have appeared as a calf with a neckerchief, a naked headless man, and even four men carrying a sheet. Some well-known brags are said to live at Picktree (where it was called the Picktree Brag) and Humbleknowe.
There is also another similar shape-shifter in Northumbrian folklore, the Hedley Kow.
In Popular Culture
Gary the Horse, from webcomic Bad Machinery, identifies himself as a brag after bucking character Shauna Wickle into water after convincing her to take a ride on his back.