I took an art class in high school and we were given an assignment to create a life size sketch of our own hand and not to sign it. The sketches were then turned in and the instructor critiqued each one. When he got to mine he used it to show how important it is to use proper proportions. I had to giggle when he said "this is a prime example of the artist not using proper proportions. The palm is wide and very detailed and the fingers are very well done also...but they do not look like they fit the palm... Your assignment was to sketch your hand as realistically as possible...NOT to make a caricature of it."
I stood up and walked to the offending sketch, placed my open hand over it and grinned as he spluttered out apologies