The RV from Hell

I still don't quite understand what compels parents of adult children to show up with as little notice as possible in an RV, and then proceed to stay there.

As I left the house yesterday I saw a big RV parked in front of our house, and for one split second I thought it was my parents. They've been threatening to "drop by" (We live in Oakland. They live in Panama City Beach, Florida), but they're not supposed to get here until AFTER JULY 27th. I have emphasized the importance of not showing up early, because while my mother understands things like Gay Pride and Folsom St. Fair, my father's reality might be a little jarred by my Dore Alley ensemble.

Last I heard, my parents were heading to my ex-wife's place to see my kids. It occurs to me that my kids are camping with the family, so it's possible that THEY DON'T KNOW MY PARENTS ARE COMING.

Why do parents do this? Is this the equivalent, in their minds, of popping into our bedrooms unannounced when we're kids to make sure we're not listening to Rock & Roll, masturbating, or worshiping the Devil? If so, my parents better HOPE they don't "drop in" early.