I bought my Grumman Cheetah in 1999 with the previous owner's "vanity" number, N116MC. Coincidentally, at an airport just three miles away there was based a Grumman Tiger, N16MC. I had lunch with the Tiger's owner one day. He suggested we fly in formation over to a nearby tower-controlled field, shoot some touch-and-goes, and play with the controller's mind.
When I painted the Cheetah in 2000, I wanted the number N121PS, but found it was one of a block of numbers reserved by Aviat for future Pitts Special production. So I went with my second choice.
Fast forward to 2007, when I ordered a new CubCrafters Sport Cub. The factory asked if I wanted a special number. I checked, and lo and behold, N121PS was now available. The Pitts Special built with that number had been exported to Canada a couple of years earlier, and now the number was mine.
About a year later, I attended a social function at the CubCrafters factory in Yakima, Washington. I was wearing a name tag with my airplane's number. A fellow attendee from Montreal walked up and said, "Hey, that number used to be on my Pitts!"
Small world.