Most elementary school teachers will have a extra desk in their class room in case they are given a new student in the middle of the year, or a child needs to sit by himself in order to quiet down, or maybe the desk will be used as a science display for the class pet.
Our empty desk is in a cluster of four other desks used for grouping students. This is the first year any class has ever said anything about the empty desk. The class I have this year has assigned it to a student named Casper.
It's not a long running, getting old joke. It's just every now and then. Someone will say, "Mr. R., Casper doesn't have a copy of the test."
Or, "Mr. R., you forgot about Casper."
I don't know who thought of it, but it sure is clever, and a first.