Selena Gomez was 9 in Barney's Best Manners: Invitation to Fun when she played the character 'Gianna'.
That was over 21 years ago in 2003.
This was her first recorded movie acting credit (although may not technically be her first actual acting role).
Today she is 31, and has starred in 49 movies in total, 45 of those since Barney's Best Manners: Invitation to Fun was released.
In Barney's Best Manners: Invitation to Fun, I think Selena Gomez looks: