A while ago, my wife set up a babysitting arrangement with her sister so that both her and her sister get approximately 1 or 2 'date nights' a month (with their respective husbands, of course). We generally take advantage of being able to go places with no child in tow, like a movie or a nicer dinner, etc.
The real fun comes on the weekends when we're babysitting though, when we get the nephews and niece.
We had the kids over quite a bit when their Mom was at girls camp. We always want to make sure the kids have a good time, so one night we gave them all popsicles to eat outside.
Doesn't that make you cringe? We took his shorts off and hosed him down before we gave him back.