A line party, which is the correct term, is basically where you gather outside of the theater in a long line waiting for the movie to open. I've been to several myself. All three Lord of the Rings movies, several Star Wars, a Harry Potter, and then LWW and PC.
Before LWW was released in theaters, someone, don't remember who, thought they should be called Lion Parties as a fun Narnian spin-off. And so they became.
