I have used the "You do know how that happens right?" on my best friend. They weren't trying and were talking about not having anymore, then boom she was pregnant. However, she is my best friend and totally knows I was joking.
I also get to use the "Oh, your so big." comment but it's more in admiration. She is two months farther along than me and I keep telling her I can't wait until I am bigger. Of course when I say "your so big." I don't say it like "OMG Your huge! Your so fricking huge!" I say it more like "awww... your getting so big..." *soft sigh*.
Anyways, so far I haven't gotten a lot of advise. But I do get told over and over "OMG your driving an hour and 45 minutes to use a birth center??? What if you don't make it?!" I just say "Ya know, my last labor was 45 hours, 32 of which were at home, if I can't make it to the BC I will be so glad I wasn't in labor for 45 HOURS!" They usually only say it once.
I also started getting told by my friends that I have finally 'popped' ie my belly popped out. But I love hearing that. I love hearing that I am actually looking pregnant in clothing, and not just fat.