No Fooling

It is a truth universally acknowledged that there is nothing more daunting than playing one of Shakespeare's clowns. 

Shakespeare's insight into the human condition might have aged well over the past 400 years, but a lot of his jokes haven't... at least those told by designated fools. A general rule of thumb is that the more times you have to look up a footnote for a joke, the more likely it is you will want to punch the character telling it. I'm always immensely impressed when actors are able to make Shakespeare's fools vibrant and amusing in performance.

Also, King Lear's Fool is totally the Fool from Terry Pratchett's Wyrd Sisters, and nothing will every change that for me.