My wife's primary school friends are all my secondary school friends. I have a few common friends also with my wife and did not know about it till they turned up during our dinner. And my wife's friend happened to be the campmate with one of my Groomsmen. When they applied for leave during reservist to attend my wedding, all 3 of them submitted the application together and their superiors were wondering if they were kidding till they produced the invitation cards together.
My dad's friend when invited to my wedding was asking my dad if I do know any friends that own a handphone retail shop because he found out that the dude who runs the shop under his block is also attending my wedding.
When I went to buy shoes, the dude at the retail outlet happened to be my distant relative and I got an additional 30% discount. When we are outside always bumped into people we know and din't realised that we actually know each other.
I was conducting an interview for an applicant the other day and she happens to be my ex colleague whom we worked together 10 years ago.
World is small. Don't do bad things. Everyone will know lol.