It's as ubiquitous every holiday season as the inedible fruitcake - and it's almost as inexplicable.
It just isn't Christmas until someone has worn one to a holiday party, or given one as a gift ... the dreaded Yuletide sweater.
You know the one.
It's got appliqued reindeer or strategically placed snowmen in festive vests. Maybe it has been overtaken by a smiling Santa Claus, or ambushed by angel-topped trees. It's green or red or cream with snowflakes. It's got choo-choo train borders, three-dimensional snowballs or gaily wrapped presents for buttons.
The "better" ones play a tinny holiday song. "Jingle Bells" is a favorite. Or better yet, they flash and glow like that famous street in Hampden.
This year, some young professionals did something daring. They embraced the holiday fashion faux pas and rescued a few lucky sweaters from the place where most go to die: the back of the closet or the bottom of the footlocker.
On Saturday, these twenty- and thirtysomethings donned the most garish holiday gear they could find, gathered a gang of friends and went on a Christmas sweater bar crawl.
They laughed and pointed. They gaped and giggled. And in the end, they found that beer is never better than when you're wearing a Christmas sweater.
"It's a funny thing," says Meghan McCabe, 28, one of the organizers of the unofficial bar crawl through several pubs in the trendy D.C. neighborhood of Adams Morgan. "But I don't think it would be as funny if we were in someone's living room wearing those sweaters. To actually be in public? That adds a little element."
McCabe and four other women from Washington and the surrounding suburbs thought it would be belly-achingly funny to wear Christmas sweaters to their favorite hangout - Adams Mill Bar and Grill - and other nearby bars. Once the Evites went out, praise for the idea started pouring in - from their female friends. Their guy friends, however, were slower to catch on.
But the prospect of partying with a group of women all bedecked in Christmas cheer was too much for the guys to pass up. And most of them finally got in on the joke.
Usually a stylish lot (they're the hip kind of crowd you read about in Washingtonian magazine), they descended on local discount stores, combed Internet sites and dug through their closets, searching for the busiest and tackiest sweaters they could find.
J.P. Fielder, 24, found in his closet the very sweater he wore to take school pictures in the third grade.
"I was a tall 8-year-old," Fielder said.
Diego Bustamante, 29, a pilot for Cape Air, bought from Stein Mart the night's unofficial favorite sweater - a blue and white number covered in a dozen carrot-sticked-nosed snowmen, some of them wearing appliqued Christmas sweaters themselves.
"That is awful," said Jill Cameron, 28, laughing hysterically at Bustamante's find.
A bar crawl organizer, Cameron ordered her jingly sweater from eBay, but was disappointed when it arrived. It had glued-on pearls, but it was saggy, she said, and the appliques were linty. Other bar-goers, she complained, looked "cute and sassy" in their sweaters, like perky elementary school teachers.
It was that kind of night. Full of sweater envy. Miller Lite substituted for eggnog. Instead of "Silent Night," Tone Loc's "Wild Thing" played merrily in the background. A woman carrying a Prada purse proudly showed off her sweater's (gasp!) ... shoulder pads.
McCabe and her friends want to do the Christmas sweater crawl every year, a plan that just might catch on, judging from the 60-plus people who showed up Saturday.
"I think it's brilliant," said Joe Bisagni, 22, wearing a red fleece sweater in a 1970s retro snowflake design. "That's why I'm here drinking beers at 4 o'clock in the afternoon."
Never mind that his too-snug sweater was a woman's - pulled from the closet of Cassie Babbington's unsuspecting mom.
Babbington, 22, had secretly raided her mother's closet for her own outfit: a navy blue cardigan with red scalloped edges and embroidered trees, snowflakes, skis, ice skates and mittens. She also borrowed her mother's tree-ornament earrings and a charm bracelet tinkling with gilded jolly St. Nicks.
"What can I say? My mom is a fan of the holidays," said Babbington.
Her mother is not the only one.
Millions of women in America love Christmas so much, they feel the need during the season to decorate everything in sight - including themselves.
Sue Cutri, owner of The Country Ewe, a clothing store in upstate New York, says she sells thousands of Christmas sweaters every year.
That's a lot of sequined appliques.
With so many Christmas sweaters in the re-gifting rotation, at least one yarn shop in New York has started a campaign to rid the world of them - offering free knitting lessons to anyone who brings in a blinking, jingling or just downright ugly sweater to be put out of its misery.
"It's surprising how people get attached to these things, no matter how ugly they are," says Kevin Lundeen, co-owner of Flying Fingers, a yarn shop in Irvington, N.Y.
Lundeen recalls one particularly offensive red, green and white sweater recently bequeathed to his shop. It was made of acrylic yarn and stitched granny squares.
"I think it was the most disgusting thing we've seen," Lundeen says.
But that sweater once belonged to a real person. Someone paid money for it. Somebody wore it.
How does a sweater go from there to becoming the punch line of an entire party's beer-exaggerated joke?
"Most people I've found don't know what looks good on them, so they don't know that they're unflattering," says "The Image Architect" Sandy Dumont, a professional image consultant who lives in Virginia. "I haven't seen one yet that made anybody look better, in terms of their figures. In fact, they end up looking hokey, so why bother?"
Unless their audience is a class full of 7-year-olds, why do the Christmas-sweater lovers bother?
Well, the sweaters are fun, says Jill Cameron, and they bring good cheer, which is one point of this season.
Bar-crawler Maureen Collins, for instance, said her holiday sweater vest - with bells on it - brought joy to the world.
Well, at least to her neighbors.
"I walked to my car, and I saw two couples who blatantly started laughing at me," said Collins, 23. "It was great."
And the sweaters also bring people together.
It happened for Laura Morris, 29. Now she and her aunt, who lives in Ruxton, have something in common: that decades-old navy blue sweater with the light blue snowflakes and the pom-pom zipper pull. Classic.
And it happened for the Christmas sweater bar-crawlers, who found an excuse to be together during the busy season, and who learned a valuable lesson amid all the scalloped collars, gold lamM-i ribbons, candy cane brooches and golfing Santas.
"You know, it's a way to get in the spirit of the season," said McCabe, in her elflike green vest and holly-bordered shirt. "And some people are able to get there more fashionably than others, I suppose."