Well, Your Honour, around the same time there was a sketch on the Harry Enfield show, in which Tim-Nice-But-Dim is introduced to a man at a party who says he's a paedriatrician, getting Tim to respond something like: "Oh gosh, I can't say I approve, but jolly good of you to be honest about it" - or words to that effect.
So if Harry Enfield saw some humorous potential in misunderstanding the word 'paedriatrician', it's quite possible the person who wrote on the plaque did too. Whether you regard it as a good joke or not is a matter of opinion, not of fact.