Running with a toothbrush is bad

Daddy got angry with me tonight because I ran down the hall with my toothbrush in my mouth. I have done it before but he didn't get as angry as he did this time. He explained that if I do that and fall over I will get badly hurt and will have to go to the hospital (where they will put the thermometer up my bottom etc etc again). Well, I agreed not to do it anymore and this pleased mummy and daddy, so I will try to remember not to.