When I get my daughter's vaccines, I have to sign once for each shot (so once for DTaP rather than three times, then once for Prevnar, and so on). So if there were two needles going into her, I would have to sign twice and each one would be marked what it was.
My doctor's office does the MA/nurse thing too. Kim is the MA who always does our intake, and it says she's an MA on her name badge, but one time she called me and left a message that started "This is Kim, Dr. X's nurse" and I was all "You are not a nurse!" Rar.