Remember the lame jokes people used to tell in primary schools? This one came to mind:
You know how people like having plate numbers that meant something? It can get quite expensive too, if the demand for a particular plate is high. Apparently, Dr. M refused to take this one, no matter how many times it was offered to him: MAT 1. And the Sultan of Terengganu refused TAH 1.
I remember seeing a PEN 15 once. I'd try to get NAB 3 if I can, though it's probably taken by now.