You're where you should be all the time
And when you're not, you're with
Some other world's spy or the wife of a postman, wife of a postman

The story:

I had been singing along about the wife of a postman for my entire life, one day I started to think how odd it was that someone would want to seduce a postman's wife........ So I stopped singing and actually listened to the lyrics. Ooopsss, unfortunately, my brothers were with me at the moment of revelation and it still comes up at family events.