Birds and Bees.

When I was four years old my mother got pregnant with my little sister. Naturally I asked how it'd happened, and she gave me an admirably matter-of-fact and unembarrassed description of the basics.

My first reaction was "Why didn't you let me watch?"

I was slightly hurt really; I felt that making my sister was an important family event, and as such, the whole family ought to have been included.