Trey Parker was 22 in The Spirit of Christmas when he played the character 'Stan Marsh'.
That was over 31 years ago in 1992.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
Today he is 54, and has starred in 35 movies in total, 33 of those since The Spirit of Christmas was released.
In The Spirit of Christmas, I think Trey Parker looks: