I'm sure you've had the experience of getting caught with an embarassing pose or facial expression in a snapshot, but can you imagine sitting days or even weeks for a painting and coming out like this?
You may not recognize this man but you've heard of him. This is the famous Dr. Samuel Johnson, the wit credited with saying "Patriotism is the last refuge of a scoundrel."
Here's another one. Some people just don't take good oil paintings.
These were both painted by Johnson's close friend Sir Joshua Reynolds so I suspect these were not without some intended humor. Sir Joshua was entirely capable of painting a flattering portrait... when he was painting himself: