Miniature Bull Terriers are equal parts muscular and mischievous, headstrong and happy-go-lucky. Originally developed in England as a smaller version of the Bull Terrier and designed to be small but stout enough to chase vermin into small spaces and tough enough to dispatch them, the breed has transitioned from a fierce ratter to a devoted companion. The Miniature Bull Terrier was classified as its own breed (that shares many of the same personality traits as the original, larger breed) in the 1990s.