Jonah Hill was 23 in Horton Hears a Who! when he played the character 'Tommy (voice)'.
That was over 16 years ago in 2008.
Today he is 40, and has starred in 56 movies in total, 39 of those since Horton Hears a Who! was released.
In Horton Hears a Who!, I think Jonah Hill looks: