Jean-Pierre Léaud was 12 in King on Horseback when he played the character 'Pierrot'.
That was over 66 years ago in 1958.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
Today he is 79, and has starred in 103 movies in total, 101 of those since King on Horseback was released.
In King on Horseback, I think Jean-Pierre Léaud looks: