I got asked this by a co-worker, but it was in his excitement because he knew I had fertility issues. I started giving him the birds and bees talk and then laughed at him. It was funny.

go to work tomorrow and bring diagrams and instructional videos on how that happens to show him

I'm pretty sure the boss actually meant how did she actually manage to have a baby, let alone get into a relationship with a man (since he obviously thinks she isn't attractive). He is basically insulting her virginity. I dunno if this is correct but it is my interpretation :)

Tell him he doesn't know because he's never done it ;)

Just tell 'em babies are delivered by the stork. Then when they eventually question where baby storks come from, you still have over a million species to choose from.

"I had sex."

Your boss is either 1.Very inappropriate or 2. Very uneducated.

Your boss is either 1.Very inappropriate or 2. Very uneducated.