In the fight scene at the party, Jake gets hit over the head with a bottle and he has blood on the top of his head. It changes constantly throughout the fight. It disappears totally when the fight is over. He has no blood anywhere on his body.
At Frankie's house, when some girls visit during the daytime, Frankie turns to Zack and calls him 'Yankele'. Yankele is a Yiddish [German-Hebrew] affectionate version for Yaakov, or Jacob, since Zack is Jewish.