My boyfriend used to live in military housing. One day, he told me that his neighbors had moved out and left a door open, and it took weeks for new families to move in. So one afternoon, we decided to take advantage of the privacy. Right in the middle of sex, what do you know... the new owners pulled in, with what looked like half a dozen children!
Good thing the front door was locked giving us a few extra seconds, we had just enough time to throw some clothes on and run as fast as we could out the side door, though I nearly lost my underwear
We still laugh about that close, and VERY embarrassing first call.