My best guess as to how Jeffery Rush can come back into P.O.T.2 is that; at the end of the credits, of P.O.T.1, there is an Easter egg that shows the monkey taking a coin from the chest. When the moon shines on the monkey he is shown to be a skeleton implying that the curse has been reactivated. Therefore, perhaps that starts the curse all over again and reawakens Jeffery Rush’s character.