Calling Homies as Saints will join the fight with you, to help you kill any gangs or cops, that comes to GTA: Underground for now, with different weapons. Calling homies is remake into Saints Row 2 style, after I played this game.

Call Homies Keys:
CTRL+SHIFT+INSERT = Call Johnny Gat
CTRL+SHIFT+DELETE = Call Pierce
CTRL+SHIFT+HOME = Call Shaundi
CTRL+SHIFT+END = Unknown Call