Keep in mind when you fight the mascot, or see him walking around, he is NOT a costume, that's the legit model.
Script-wise, he is declared as a jock. You can find this from either Hex editing the ide.img or looking in default.ide. here is his info:
88 Player_Mascot Player_Mascot_W 0 Medium JOCK STAT_J_MASCOT Straf_Male B_Striker null null -1 /Global/J_Mascot Act/Anim/J_Mascot.act /Global/AI Act/AI/AI.act N_Mascot