Alan Arkin was 27 in That's Me when he played an uncredited character.
That was over 60 years ago in 1963.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
Today he is 89, and has starred in 95 movies in total, 92 of those since That's Me was released.
In That's Me, I think Alan Arkin looks: