The suspect got his nickname because he appeared to be chewing tobacco during one of the robberies, although authorities suspect he may have a medical condition.
The suspect typically hands a yellow note through the teller's window. He's described as a white man in his 50s, about 5 feet 5 to 5 feet 7 inches tall and weighing between 160 and 170 pounds.
Anyone with information about his identity or whereabouts is being asked to call the FBI at (888) 226-8443, or the LAPD.
City News Service contributed to this story.