Talk to anybody who's grown up with identical twins, and you'll find that the differences between them are evident from a very early age -- personality as well as physical characteristics.
Here's another one: for about 20% of identical twins, one is right-handed and the other is left-handed. (I knew a couple of guys in college who had this characteristic.)
Based on the number of Google hits, there's obviously a lot of interest in the differences between identical twins....
I wonder if the right and left handed twins are what they call mirror image twins.
I have identicals myself and they have had very different personalities right from the start even though they look very much alike.