Starring Reese Witherspoon and Vince Vaughn. Rated PG.

Apparently, the only thing worse than a dysfunctional family holiday is a movie about dysfunctional family holidays. And Four Christmases is four times worse than the usual “comedy” awash with Yuletide bile.

The cast here did offer some promise. Starring as self-absorbed, unmarried, and childless San Francisco couple Kate and Brad, Reese Witherspoon and Vince Vaughn have a nimble-tongued, easygoing repartee that compensates for their lack of obvious chemistry. Their detached brand of egotism is probably what helps this screen couple get along so well—something put to the test when their usual escape plan falls through and they’re forced to spend Christmas day at the homes of their divorced parents.

These participants include his ornery, redneck dad (Robert Duvall), extreme-fighting brothers (Vaughn pal Jon Favreau and country singer Tim McGraw), and genteel mom (Sissy Spacek), now living with one of his high-school buddies. On Kate’s side, Mom (Mary Steenburgen) has become a sexed-up Christian; her sister (Kristin Chenoweth) keeps popping out babies—hence the hilarious projectile vomiting that dominates the flick’s trailers. And barely seen Dad (Jon Voight)—well, the 82-minute movie has run out of steam, if not bodily fluids, by the time we get to his place.

Basically, this is a string of uninterrupted traumas, with physical abuse and dark childhood secrets vying for primacy in the hall of shame. It’s Open Water, with the sharks replaced by drunken family members. But in this disappointing mainstream debut for doc director Seth Gordon (The King of Kong), working from a committee-written script that’s been kicking around for years, the film’s tragic qualities are simply treated as more validation for yuppie love. In the end, these reptiles must replicate. But they are only in it for the shopping.