I think about this all the time: who could play the younger version of who. Now there is a Tumblog called Kid Casting:
This is pretty amazing casting: I totally forgot that the young Mila Kunis played the young Angelina Jolie in Gia.
And here's another feat: witness the young Mayim Bialik (Blossom) as the young Bette Middler in Beaches.
Here’s my screen doppelganger: jazz singer Molly Johnson. Oh, and maybe one of these kids (scroll down) could appear as the young me. What a strange and fuzzy-haired world that would be.