I was three years old when I had my tonsils out. The way they did it at the hospital I went to was all the kids getting tonsillectomies stayed overnight and the operations were done early in the morning, production style. The night before my tonsillectomy, I remember my mother telling me to go to sleep in the hospital crib and not worry as she would be upstairs drinking coffee while I "napped." I recall an interaction with a nurse during the middle of the night and I also recall the car ride home from the hospital and getting a stuffed animal from my aunt the next day after the tonsillectomy. It was obviously a pretty traumatic/important event for me. Other than that, the next oldest memory I have from when I was 5-6 years old and in first grade.
I remember going to the doctors at a young age to get a shot and remember going to Toys-a-rus afterwords since I had behaved very well (or was it a bribe to get me to go in the first place? )