Jean Dujardin was 27 in Un gars une fille - Vol.1 - Les Tribulations de Chouchou et Loulou when he played the character 'Jean'.
That was over 23 years ago in 2001.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
Today he is 51, and has starred in 66 movies in total, 64 of those since Un gars une fille - Vol.1 - Les Tribulations de Chouchou et Loulou was released.
In Un gars une fille - Vol.1 - Les Tribulations de Chouchou et Loulou, I think Jean Dujardin looks: