His friends won't believe what a prize idiot he has located. But then, Pierre hurts his back and must cancel out of the dinner party. Mr. Pignon visits him anyway, trying to help his newfound friend. In short order, the idiot has turned Pierre's life upside down, humiliating him and almost ruining him on every front from the romantic to the financial. As Mr. Pignon, Jacques Villeret carries this comedy on the strength of his bumbling.
Every plan goes awry.
Every bit of help he offers Pierre backfires. Lhermitte and the rest of the cast are occupied mostly with reaction. Initially, the movie is cruely funny and quite sophisticated. The idea of grown men searching out idiots in a competitive fashion is, of course, deeply offensive, and also quite a wonderful comic premise. Once The Dinner Game moves indoors to Pierre's lavish apartment, it doesn't really have anywhere to go, except to sitcom territory.