Staffordshire Bull Terriers are the original Staffies from the United Kingdom. Once brought to America, the dogs were bred to be so much larger, they were separated into a different breed by the kennel clubs; the American Staffordshire Terrier. The adult Staffie is smaller overall, but also has slightly bowed legs, and for the body size has shorter legs and a wider chest. The Staffie and AmStaff share the Pittie Personality, as you can see from this little smiling gal Abby.
Abby also makes the strangest dog noises ever; check it out.