Remember the first dog we had. Runt of a bull terrier, we had a HUGE tire (in reality, probably 14 inch from a gemini or something) that we used to roll down the yard for him to chase/catch/do two full revolutions with before it'd slow down. He went when I was 2 1/2.
2nd memory I have is me being bulldozed by the 2nd dog we had. He was about 38kg, a big fella, rock hard skull, I cried.