Mr. No Brain
If you are a teacher named Mr. O'Brian, it's not a good idea to introduce yourself to a class by telling them that the name 'Mr. No Brain' is not funny as you write 'Mr. No Brain' on the blackboard.
written by an*nymo*s use*, approved by Phil

Similarly, the ludicrously diminutive Mr Hughes told his form class on the first day NOT to call him Mr Huge, as it really, really wasn't funny. The result was as predictable as night following day.
written by Em*Bird, approved by Conor

"My name is Mr. Reese. Don't call me grease!", snapped Mr Reese one day. To be honest, the thought had never occurred to us, so it was good of him to make us aware of the possibilities.

More than earning himself a new nickname, Mr Reese's outburst had such a satisfying rhythm to it that it quickly became a popular playground chant.
written by an*nymou* u*er, approved by Log