What if the Korban Pesachs were jumbled, and one of them was rendered problematic. Now what? A "residual korban" might be a good solution, though how that would work is also a good question. Also, the laying on of hands for the korban, a distinction between the Korban Pesach and a korban shelamim (for men, anyway). Also, when a father apportions the Korban Pesach to "the child who gets to Jerusalem first" - whether that's "bereirah" (retroactive clarification) or a father's pedagogical tool. Also, registration for a Korban Pesach stays open as long as there's a k'zayit for each person. Also, one who registers for a Korban Pesach, and registers a buddy too, without the rest of the group's approval. Plus, one who takes more generous portions for himself... the halakhic implications to the very human complications of sharing a meal.