Well i have theories to explain the behaviour of some of them stupido Nerazzuro!
Vieri - Grew up in Australia, which explains his competitiveness (which cost Maldini a broken nose) also his natural aptitude for goofyness can also explain that
Cordoba - Born n' raised in Medellin (which is officially the most dangerous city on Earth - with murderers, rapists and drug dealers running around everywhere) so he would have to be tough as a youngster to grow up unscathed from his city... which can explain his dangerous and tough guy attitude which he used to 'hurt' serginho..
However, i cannot explain why Materazzi is such a jackass.. i do not know much about this guy, but now i think he is just an untalented, frustrated idioto