Madison Pettis was 8 in Horton Hears a Who! when she played the character 'Additional Voices (voice)'.
That was over 16 years ago in 2008.
Today she is 25, and has starred in 24 movies in total, 21 of those since Horton Hears a Who! was released.
In Horton Hears a Who!, I think Madison Pettis looks: