Steve Martin was 9 in Disneyland Dream when he played an uncredited character.
That was over 67 years ago in 1956.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
Today he is 78, and has starred in 106 movies in total, 105 of those since Disneyland Dream was released.
In Disneyland Dream, I think Steve Martin looks: