I'm only on baby three and I get those questions from my family (when they aren't pretending not to remember I'm preggo and thinking that's funny. "Are you pregnant or something? You're kinda fat.."
When I'm asked;
"Are you done yet?"
My answer, "Well, I'm trying to fill up the van. After this one we only have two more seats to fill!"
They go ballistic and I just laugh at their reaction.