Leonardo DiCaprio was 13 in Mickey's Safety Club: Street Safe, Street Smart when he played the character 'Alex (voice)'.
That was over 35 years ago in 1989.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
Today he is 49, and has starred in 66 movies in total, 59 of those since Mickey's Safety Club: Street Safe, Street Smart was released.
In Mickey's Safety Club: Street Safe, Street Smart, I think Leonardo DiCaprio looks: