The Grand is a shaggy-dog poker spoof graced with a considerable cross-section of American comedians, but given its nature as an exercise in improvisation, it’s anything but what the title suggests. Zak Penn, who directs, calls the dialogue a “scriptment”—by which he means that he issued the actors “information that the production needs,” but gave them their heads to work out the one-liners. The film will likely attract the people who, strangely enough, get their kicks from watching live poker on TV, just as dog people were the most likely audience for Christopher Guest’s Best in Show and fans of rock music might be able to laugh at themselves while watching Rob Reiner’s This Is Spinal Tap.

As mockumentaries go, however, even Michael Moore’s principal dud, The Big One—a comic turn at the book-tour circuit—might be considered a flush to The Grand’s pair of deuces. The film, which gives A-class movie comics a chance to strut their stuff without aggressive direction, has two segments. One part provides a look at the offstage lives of some of the players, suggestion their motivations in entering a poker tournament—though the winner’s pot of ten million dollars would seem to be an adequate incentive all by itself. The second segment gives us ringside seats at the poker table, a game which is watched by scores of people shown in the background while those watching on TV have the advantage of hearing and watching two announcers displaying each contestant’s hand while the game is in progress.

Ultimately, Penn hopes we’ll get to like at least some of the players, rooting for our favorite to win: The gimmick is that the conclusion of the game, like the rest of the movie, is unscripted—the prize goes to the person who actually emerges victorious.

Which ones will be your favorites? Chris Parnell (“Saturday Night Live”) in the role of Harold Melvin—who still lives with his mother Ruth (Estelle Harris)—is plain irritating and unamusing. His shtick is to talk like a computer, in pure monotone, and utter aphorisms to Ruth like “If I were a food critic, I would give your cooking five stars—five stars that have each collapsed into a black hole and merged to form the largest black hole in the universe.” His character is allegedly based on a real person with Asperger’s Syndrome. Woody Harrelson is somewhat less annoying as intoxicated ex-champ One-Eyed Jack Faro, who seeks to recover his fortune and save the casino from demolition. Filmmaker Werner Herzog shows his comic side as a loud, animal killer and card pro who threatens the future of the game in a rant when accused of cheating.

The best sight gag finds David Cross (“Arrested Development”) as Larry Schwartzman, who sports a full-scale hijab, insisting to the referee that “I converted to Muslim last night.” Anthony Hardwick’s lensing gives us the view from inside the attire, allowing us in the audience to pity the poor women of Afghanistan who go through their adult lives as though peering through a periscope.

Among the small pleasures are the play-by-play announcements and ideas floated by the TV commentators, Mike Werbe (Michael Karnow—who was on the crew of the Discovery in Penn’s previous mockumentary, Incident at Loch Ness), and Phil Gordon as himself. (Gordon placed fourth in the 2001 world series of poker.) Werbe gets to plug his book Winning Is Winning, a title presumably meant to evoke laughs. The most likeable person, Lainie Schwartzman, is played by Cheryl Hines (“Curb Your Enthusiasm”), determined even more than the men to win the games and the ten mil.

The entire film is just too low-key and bland to stir enthusiasm. Nonetheless, we’re told that this was a favorite last year’s Tribeca Film Festival.