It's finally happened.
I began receiving some of the obnoxious comments parents of larger families tend to get, along the lines of, "Can't you keep it in your pants?" The obnoxious comments came at work, in the spirit of a joke, and caught me off-guard. I'd told myself I'd be ready with something witty if it ever happened to me - alas, I just smiled and said nothing at first. My brother has had some very effective responses (I'm not sure if he's ever actually used them, or just told them to me). For example, in response to, "Don't you know how babies are made?" (or some version of that), his retort is, "Yes, we do. And we quite enjoy it."
In the hope that this type of humour comes quickly to my mind and my lips, should this occasion befall me again ....
Feel free to drop your reply quips in the comments (or if you're daring, your nasty comments that you'd like to direct to parents of large families).