I had twins born just over 10 years ago, and can clearly remember the doctor pulling up the ultrasound and circling a little dot and calling it a baby. There was another dot just like it on the other side of the screen, and I thought "this guy has no idea what he's doing", because he was missing the other dot.
Then he said, "here's another one". I said "another what?" He looked at me, and calmly replied, "there are two babies in here. You're having twins."
At that point, everything changed. Nobody believes me, but I bet you do. And everyone else on this thread who has kids gets it, too.
I had a boy and girl; the boy is named Henry. Small world, brother.
Keeping with the hacker theme, my kids are easily the best products I have ever shipped. :-)