Good Comebacks for when People Say Dumb Sh...Stuff

My husband, T, is the king of comebacks.  You know why?  Because he really, REALLY doesn’t care what anyone thinks of him.  Me?  I’m terrible.  I’m that person who thinks of the comeback two or three hours later.  The only time I was remotely good at it was when I was pregnant and grumpy. 
You know what people say the dumbest things about?  Pregnancy, post-partum stuff, parenting, and other people’s relationships.  What do these things have in common?  They are NONE OF YOUR DARN BUSINESS. 
Some of my favorite stupid things people have said [these are real; names changed to protect identity] and my suggested comebacks:
“Oh my, your little Bobby is such a brat.  I don’t know what you are doing wrong.  My daughter, Susie’s little boy is such an angel.” 
Yeah, I trust your judgment ‘cause you did such a fabulous job raising Susie. 
Oh, Bobby only acts like that when we don’t give him his daily dose of marijuana. 
“You look good.  Your belly is getting smaller.  But I’m not saying your skinny.  You left your days of being hot behind in college.”
At least I got to experience being hot.  You poor ugly idiot.
“You are definitely a lot bigger than last time [you were pregnant].”
You are also a lot bigger than….oops.  Sorry about that.
“You should bite him [your son] back when he bites you.”
How about I bite you, you moron?
And the classic dumb comment, said to a newly married couple: “When are you going to start having kids?”
For the comebacks to this classic, I must once again credit my newly married colleague, Jay L.  His suggestions are much better than mine:
When they relax the child labor laws.
About 9 months and 15 minutes from now. Will you excuse us?
We'd like to, but there was this bowling accident a few years ago...
As you can see, mine are pretty lame compared to Jay's.  Help me out, whatcha got for comebacks?

The Globe Guardian has some doozies. 

Aunt Kay [aka, “The Light”], if you are reading I know you will respond with something like “Sweetie, take the high road and just tell them how wonderful they are.  Thank them for the advice and go on your merry way.”  If I promise to do that and just think these great comebacks, will you forgive me?