Delightful apart but deadly together, Reese Witherspoon and Vince Vaughn look, throughout "Four Christmases," as if they just want to get this thing over with.

That their characters spend the film with family members they would prefer to avoid is coincidental. The true awkwardness lies in the pairing of movie stars.

Wrong for each other physically, comically and perhaps even spiritually, the tiny, self-possessed Witherspoon and her tall, anything-goes co-star seem randomly matched in the way stars no longer required to screen-test together (e.g., Matthew McConaughey and Sarah Jessica Parker, "Failure To Launch") sometimes can be.

From this mismatch to its lowbrow script, "Four Christmases" smells of faulty Hollywood packaging. The best the picture can say for itself is that it's only Vaughn's second-worst holiday movie, after "Fred Claus." There's rarely a smart moment in "Four Christmases," and that's a disservice to its stars, whose one shared trait is intelligence.

Instead, the picture gives us pratfalls, projectile vomiting and far too many opportunities to embarrass Witherspoon, an actress of considerable dignity, not to mention the owner of an Oscar. (Frankly, when watching "Four Christmases," "Walk the Line" seems to have happened a lifetime ago.)

Directed with little flair by Seth Gordon, maker of the excellent documentary "The King of Kong: A Fistful of Quarters" (seriously, rent it), "Four Christmases" is an episodic film strung together by an interesting enough premise: Brad and Kate, a San Francisco couple who prefer spending holidays on exotic isles, are fogged in at the airport and interviewed by a local TV station for a segment subsequently viewed by their respective (divorced) parents. Thus, they are unable to extract themselves from visiting four separate households and meeting each other's relatives for the first time in their three-year relationship.

What kind of relationship lasts three years without the participants meeting each other's family members, especially when everyone lives in Northern California? The kind that happens only in the movies, of course. Sort of like a scene where Brad and Kate take the Golden Gate Bridge to get to the airport from San Francisco.

First up is Brad's father's (Robert Duvall) rural, hick- ified home, where Kate and Brad enjoy cheese product on trans-fat crackers and Brad gets pummeled by his cage-fighter brothers (Tim McGraw and Jon Favreau).

Though the movie's depiction of lower-middle-class life is condescending, production designer Shepherd Frankel certainly nails the details, from the gold stove to the 1970s casserole dish Brad's parents probably saved S&H Green Stamps to obtain.

Able to be crinkly and ornery by rote, Duvall, like most of the top-drawer supporting cast (Sissy Spacek plays Brad's mom, Mary Steenburgen is Kate's mom and Jon Voight is Kate's dad), breezes through his role. Expending considerably more energy are Favreau, Vaughn's pal and frequent co-star, and Katy Mixon, who plays his character's wife. They perform a well-timed, wonderful bit of comedy during a gathering at Brad's mother's upscale hippie pad.

When Kate and Brad visit the well-tended suburban home of Kate's mother, Kate is the brunt of all jokes, with Witherspoon asked to physically battle 5-year-olds and withstand baby spit-up and the upstaging of her character by her boyfriend.

The scene where Brad outshines Kate is funny, showcasing Vaughn's agitated-showboat charms. But it doesn't help explain why Kate subsequently would nudge Brad, a commitment-phobe as well as an attention hog, to marry her.

Witherspoon seems to wonder the same thing, bringing a joyless quality to relationship-centric scenes as well as to more comedic moments.

Call Bee movie critic Carla Meyer, (916) 321-1118. Hear her discuss the week's movies at 4:40 p.m. on Fridays on NewsTalk 1530 (KFBK).