Here’s a tip to keep in mind when deciding whether or not to see a new movie: If there are more than two writers credited, be afraid. Be very, very afraid.

"Four Christmases" proves that when it comes to screenwriting, too many cooks in the kitchen makes for a barely digestible movie. This holiday clunker is a disjointed mishmash of scenes held together by a plot thinner than Scotch tape.

Brad (Vince Vaughn) and Kate (Reese Witherspoon) have dated for three years, yet they have managed to avoid visiting either of their families for Christmas ("You can’t spell ‘families’ without ‘lies,’" they say.) Their streak ends when their plane out of the country is delayed and they are interviewed by a television reporter.

Their families see them on the tube, and now there’s no lying their way out of visiting all four of their parents’ homes in one day.

As we meet their variously odd kin, we understand why Brad and Kate have avoided them. But we also learn that Brad and Kate have not been honest to each other, either, and they have such a great relationship only because it has never been tested. They have shirked any long-term commitments and live in their own self-indulgent world. The extended honeymoon ends when they endure the stress of a family holiday.

The scenario is as formulaic as it gets, but this movie could have been something.

For one, this is one of the better casts ever to appear in a holiday movie, including Robert Duvall, Sissy Spacek, Jon Voight, Mary Steenburgen, Jon Favreau, Kristin Chenowith, Carol Kane and Colleen Camp. Even Dwight Yoakam and Tim McGraw show up, but like most of the cast, they are given nothing to do.

Rarely has so much talent been so completely wasted.

At times, the writing shows promise. While visiting the home of Brad’s mother Paula (Spacek), the whole family plays a board game. Something as silly as a game causes sibling rivalries and other unspoken tensions to boil over, which is a situation many have been in. And it’s funny without resorting to bodily function gags. That moment gives us a glimpse of the movie that might have been.

Instead of more good writing, though, we get two vomit jokes, a breast pump gag, characters falling off roofs and a ridiculous battle royale in an inflatable castle.

The low point of the whole mess, though, comes when Brad and Kate attend a church service with Kate’s mother. The church members cast as Joseph and Mary in the Christmas nativity play cancel at the last minute, so naturally the pastor pulls Brad and Kate, two visitors whom no one knows, into the play.

Kate gets stage fright but Brad hams it up, going off script and whipping the congregation into a frenzy with a bunch of nonsensical jibberish cribbed from what little he knows of the Bible. The entire scene insultingly stereotypes Christians as mindless zealots, it is completely implausible, the acting is embarrassingly bad — and it is just plain stupid.

"Four Christmases" could have captured the anxiety everyone feels around the holidays, which offers plenty of laughs, but it instead punishes us with one idiotic scene after another.

The big box office numbers the movie has posted mean only one thing: A lot of people saw a very bad movie last week.