The cover shows Stewie carrying the Freezing Rifle. Actually, the only character who can use the Freezing Rifle is Brian.
In the boss battle against Long John Peter, Peter jumps on the player's boat to fight Brian/Stewie. At the same time Peter can be seen in the other boat with his men.
In Santa Claus' office, a Menorah (seven-branched lampstand, symbol of Judaism) can be seen. But in the episode "Road to the North Pole" (which the Christmas level is based on) Santa claims on his deathbed that "he will be with Allah soon", meaning he is Muslim.