This topic always makes me LOL.. I think back to our newlywed days when something I did "cured" my new MIL from her habit of just dropping in and she must have spread the news, 'cuz suddenly, noone on his side of the family would just show it, it was always at least a call saying they were in the area and could they stop by...
we have 2 bathrooms (very little house that was built in the early 60's so the original bathroom (main bath) is barely big enough to turn around in. At some point, the previous owners added on a bathroom to the master bedroom, so that one is at least a little bigger.. anywhoo... not only would my MIL just 'show' up, but when she had to use the restroom (and thats pretty much always) she just HAD the use the one in our bedroom cuz she said she fit better (she is a little large so I really do get this, but it annoyed the heck out of me cuz I always felt like 1/2 the time she was just snooping!) so one time when she just showed up, I talked to her for a few moments & then left her with DH while I went to our room for a few moments to "set the stage" I pulled out a box of all the "teddies" and fur and handcuffs and lotions and potions we had gotten at my various bridal showers etc and just sort of staged them all over the room/bed etc (you know handcuffs from the headboard etc) and then I went back out... well, as typical, a bit later, she just had to go to the restroom, and of course, just had to use ours... boy... she was not in that room 2 seconds ( I know she never made it to the restroom) and practicaly ran into the den, with a bright red face and excused herself and left... that was the last time she showed up unannounced... I guess she didn't like seeing all our "toys"

I still get a good giggle out of that 14 years later!
I love company, don't get me wrong. But I also work 40 hours a week and my kids do tae kwon do, soccer, etc and add in Dr appts and vet appts and just general housework and yard work, and I don't have much "free" time and I do hate it when someone just shows and I was planning a quiet eve or something..