Isla Fisher was 31 in Horton Hears a Who! when she played the character 'Dr. Mary Lou Larue (voice)'.
That was over 16 years ago in 2008.
Today she is 48, and has starred in 34 movies in total, 20 of those since Horton Hears a Who! was released.
In Horton Hears a Who!, I think Isla Fisher looks: