Prompted by a discussion I was having with cstanton - and you'll have to trust me that this is how it started, and not that I was duped into one of these - I was intrigued to know of any Fool's Errands which you may have been on the giving or receiving end of in your time.
There's some common ones, such as asking an apprentice or new team member to fetch a left-handed screwdriver, tartan paint or a glass hammer, but that got me wondering if there's some examples that you may have come across in your particular fields.
Let me know, as I'm keen to avoid them all!