Way back, when I still lived in Ireland, I was walking with my dog Chico off lead in a local park. He liked to run and greet all the other dogs in the park, but was always well behaved, if not 100% perfectly trained. He ran towards a lady with some little designer breed dog - she picks up her dog, holds it up in the air and basically panics, yelling as if Chico was gonna eat her and her pup (all before Chico had gotten anywhere near her). All this excitement, plus the fact that the poor dog was now up in the air and barking his little head off, got Chico very excited, but one call from me, he turned, ran back to me and sat in a perfect heel position while I attached his lead, then walked away calmly.
Chico was a jack russel cross and only a little bigger than the dog she had and certainly never showed any signs of aggression. I was so chuffed at my perfectly behaved dog and even more so at the fact he showed off to the lady who saw a slightly scruffy crossbreed and made an assumption.