The Origin Ball is the only usable Poké Ball that is also a Key Item, and the only kind of Poké Ball obtainable in a core series game that cannot be thrown during normal gameplay.
The Origin Ball can only legitimately contain two species of Pokémon, the fewest of any Poké Ball in the core series games.
Due to this, Dialga and Palkia are the only two Pokémon that can be legitimately caught in every kind of Poké Ball in the core series (besides the Park Ball, which cannot be the registered Poké Ball of any Pokémon).
The Origin Ball is the only type of Poké Ball that Pokémon can be caught in which does not have a corresponding challenge in Pokémon HOME requiring Pokémon caught in it to be deposited.