Alfonso Cuarón was 38 in Behind the Scenes of 'Y tu mamá también' when he played the character 'Self'.
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 62, and has starred in 6 movies in total, 5 of those since Behind the Scenes of 'Y tu mamá también' was released.
In Behind the Scenes of 'Y tu mamá también', I think Alfonso Cuarón looks: