On the way back from Intercon MidAtlantic, we stopped to eat at a Bob Evans. The women's room there had a small sign explaining how to wash one's hands, and suggested timing it with a verse of "Old MacDonald Had a Farm". The sign even included the words to a full verse of it, which I thought was mighty friendly.
Of course, my memory of that song, for many years now, has been of Musical Chairs' performance of it. I think it was Musical Chairs, not Technical Difficulties. Whichever group it was, I sat listening to it. I was sitting on the floor. I laughed so hard that the general consensus was that I fell off the floor. So, that's the version of the song I use for hand washing.
It's "Old MacDonald". Well, it's "Senex MacDonald". I have a much easier time singing it in Latin.