Alyson Hannigan was 11 in Impure Thoughts when she played the character 'Patty Stubbs (as Allison Hannigan)'.
That was over 37 years ago in 1986.
This was her first recorded movie acting credit (although may not technically be her first actual acting role).
Today she is 49, and has starred in 27 movies in total, 26 of those since Impure Thoughts was released.
In Impure Thoughts, I think Alyson Hannigan looks: