Another day, another shot

The other day I had my 4-month check-up at the baby clinic. I am 15 and 1/2 pounds and 25 inches long. Just for kicks, I did my rolling over trick for the doc and got the reaction I was hoping for - ooh's and aah's. She even said she wishes all babies could be like me. But she still gave me an injection. Does that mean she wishes all babies could be pincushions? What does a babe have to do around here?? Adults - I don't get them.