One day, Little Johnny visited…

One day, Little Johnny visited a doctor for a vaccination. After the doctor gave him an injection, he tried to bandage around Little Johnny’s arm.
“I think you’d better bandage around the other arm, doc!”, said Little Johnny.
“But, why? I’m supposed to bandage around the injected part of your arm to let your friends know not to touch it.”
“You really don’t know anything about how my friends behave!”