In the canon of Christmas songs, there are standards ("Rudolph the Red-Nosed Reindeer"), staples (anything by Bing Crosby, "Do They Know It's Christmas?," Eazy-E's "Merry Muthaf---in' Xmas"), novelty numbers (Elmo & Patsy's "Grandma Got Run Over by a Reindeer"), avant-garde choices (the Pogues' "Fairytale of New York," the entirety of Sufjan Stevens'Songs for Christmas collection) and tunes that just defy classification (Run-D.M.C's "Christmas in Hollis," anything Mannheim Steamroller and Trans-Siberian Orchestra have churned out).

And then there are songs like "Last Christmas," a harmless, inconsequential holiday ditty released in 1984 by Wham!, the British pop duo comprised of a pre-Faith George Michael and a pre-obscurity Andrew Ridgeley.

The song itself is fairly unremarkable: a Christmas song that's only superficially about Christmas, containing little more than four-plus minutes of gauzy synth lines, breezy vocals and even more breezy lyrics about holiday heartache ("Last Christmas/ I gave you my heart/ But the very next day you gave it away").

In fact, it wasn't even the most popular Christmas song released in 1984 (that would be the aforementioned charity blockbuster "Do They Know It's Christmas?"). And yet, in the 22 years since it hit the airwaves, "Last Christmas" has become one of the most-covered Christmas tunes in recent memory, with more than 200 artists paying tribute to its, er, majesty.

Why? We have no idea.

And neither do Alex Liebold and Adam Cote, the masterminds of Last-Christmas.com, a Web site dedicated to collecting the best of those covers. Since launching on December 1, the duo have posted 135 different versions of "Last Christmas" -- with a total running time of well over nine hours -- for, well, for whatever reason.

"In the simplest sense, this project began last year when I was trying to find holiday songs to play at work, and I was shocked to find more than three versions of 'Last Christmas,' " Liebold told MTV News. "It's just a ridiculous concept. Finding four versions is really funny, and eight versions is funnier still. It became almost compulsive to find one more ... and then one more.

"But in discussing my collection with others, there seemed to be a complete lack of understanding as to why the song had so many iterations. Few would claim it as their favorite song, and few would say they hated it," he continued. "It just happens to be on everyone's holiday mix, whether they like reggae or trance or explicit squirrels. In a more academic sense, perhaps its popularity comes from its unobtrusiveness: It is obviously related to Christmastime, but only superficially; it is both hopeful and spiteful; it's musically interesting but not difficult to perform."

Um, exactly. And despite (or perhaps because of) the song's "unobtrusiveness," the site has already compiled an impressive who's-who of "Last Christmas" coverers, a list including but not limited to Jimmy Eat World, Carrie Underwood, Travis, Crazy Frog, the Manic Street Preachers, Erlend Øye, Mr. Methane (whose flatulence-heavy version is truly, uh, breathtaking) and the Cheetah Girls. And thanks to visitor submissions and suggestions, that list is growing daily.

Of course, with the ever-growing list comes ever-growing responsibilities, and Liebold claims the duo -- who work together at a social-marketing firm in Providence, Rhode Island -- spend between two and three hours a day working on the site. And the majority of that time is spent debunking various visitor-generated myths about artists covering "Last Christmas."

"No matter how many times we say it, the Beatles never performed a version -- it's amazing that people think that," Liebold said. "Also, people have a hard time believing that the Human Nature version is not 'NSYNC or the Backstreet Boys. So we compiled a list called 'Artists That Have Not Covered "Last Christmas," ' both to help out, and as a non-confrontational way of encouraging those artists to cover the song."

And despite the mounting headaches, Liebold and Cote remain fascinated by the appeal of "Last Christmas" and plan on updating Last-Christmas.com with new versions of the song until December 25, when they'll have posted somewhere in the neighborhood of 175 different renditions. Though, much like the song's appeal, they can't really explain why.

"We've asked ourselves that question ever since we started," Liebold said. "Why are there even three different versions [of the song]? Or eight? Do the artists not realize how many versions exist and think they're doing something new? And what made 'Last Christmas' a holiday classic in the first place?

"We're gonna have over 175 versions, at over 10 hours of playing time, when this whole thing is done," he concluded. "Not too shabby for a 20-year-old song."