Look inwards Mr Pi, see your self as you are and then you can be the change you wish to see.
AKA - stick a camera on a Pi, point the camera at the Pi, set it up to take regular pictures, compare them against previous pictures and log/alert someone if there is any change.
I said this was a silly idea, right up there in the title. Not quite as philopsophical as
cat /dev/zero > /dev/null but it's getting there.
Also, if the Pi does notice itself changing, it's probably good to have it programmed to alert you rather than carrying on with its evolution (or nascent self-awareness) quietly.
Alternatively, it could be quite self-affirming. Little Pi gets to see what it looks like and see if anything it does makes it look any different.