I never had this happen and never would have wanted it growing up, but despite that it's a very strong fantasy for me, wishing I could have been that cool with it.
I tend to do it with make-believe friends rather than remember real ones, although I admit there is one friend I do sometimes think it would have been cool to have there, and double the fun for me watching him get examined (yes I had a crush, I'm pretty sure I imagined that scenario when we actually were kids although didn't quite know why I liked it so much. All part of how I 'knew but didn't know' about my sexuality.)
I guess I sort of got one stage away from this in that for a while as a kid I was looked after for a few hours ‘after school’ by a family my parents were friends with, and whose kids I was also at school with (a typical childcare arrangement when I was growing up because of parents' work hours) and on a couple of occasions I remember my friends' mum picking us up and saying ‘We’re going to the doctors' and I remember thinking ‘Just relax, you’re not going, you've just got to sit in the waiting room while they go' and that turned out to be right.
Their mum went in with them one by one leaving me and my friends to look out for each other in the waiting room. I actually remember imagining ‘What if I was sick one day and my friends’ mum actually did have to take me in to see the doctor?' It was a scary thought at the time, and embarrassing to think about, especially if the doctor got a stethoscope out and asked me to take my shirt off, but in hindsight I know my friends' mum would have been brilliant in that situation and my own parents would have completely trusted her to do that for me if it was ever needed.
Kid-me would have put up one hell of a wall about it, but I actually think I might just have been persuaded to run with it if I knew in advance that my parents thought it was okay. If any of her kids had gone in with me I actually think they'd have been pretty cool about the whole thing too.