From reality-show novelty songs to stocking-stuffer EPs, Christmas isn't Christmas until two people who have no business being in the same room have crowded in front of the mic to sing a holiday classic. Why do they do this? You should just as soon ask Black Friday shoppers why they camp out for hours in front of big-box stores. Holiday magic is a compelling thing.
Below, find our choices for the 10 strangest holidays duets of all time:
10. Rod Stewart and Cee Lo, "Merry Christmas, Baby"
Two of the most unique vocalists in pop teamed up for this performance at Cee Lo's 2012 Christmas special. (A studio version also appears on the pair's Christmas albums, Cee Lo's Magic Moment and Merry Christmas, Baby.) Both of these guys can get crazy, but – perhaps because kids were watching – they toned it down to cover the Johnny Moore classic. Cee Lo's wail and Rod's rasp have never sounded more similar.
9. Susan Boyle and Elvis Presley, "O Come, All Ye Faithful"
Not just anybody gets to duet with The King, as the Presley estate has high standards when it comes to letting Elvis posthumously share the mic. Susan Boyle must have seemed like an unconventional choice – she's the exact opposite of a hip-swinger – but she proves a properly respectful duet partner. As in all of her covers, the Britain's Got Talent alum approaches the original with a religious reverence.
8. The Flaming Lips and Yoko Ono, "Atlas Eets Christmas"
This one's a special kind of weird. The Flaming Lips and Yoko Ono are the only group on this list that you can actually imagine hanging out together – even if whatever you imagine them doing is undoubtedly less crazy than what they actually do in real life. (Poetry slams? Shadow-puppet contests? Water-skiing – on the moon?) We're not quite sure of the plot of "Atlas Eets Christmas," but put it on in the background and it sounds almost like a normal Christmas carol.
7. Mary J. Blige and Jennifer Nettles, "Do You Hear What I Hear?"
Country and R&B often seem like jokes to each other's respective fan bases, but the two genres have plenty in common, starting with their love of big-voiced divas. Mary J. Blige and Sugarland's Jennifer Nettles have made a habit of crossing these genre lines together – they both played the Christmas in Washington concert in 2009 – but the high point of their collaboration came at the 2013 CMA Country Christmas telecast, where the duo's heart-shaking harmonies on "Do You Hear What I Hear?" stole the show.
6. Celine Dion and R. Kelly, "I'm Your Angel"
This wasn't always a strange pairing. Before he was a pop-culture punchline, R. Kelly was mostly known for soft, syrupy ballads – the very kind that Céline Dion rode to the top of the charts in the late '90s. The two made for fine bedfellows on this cut from Dion's 1998 Christmas album, but subsequent events have taken these two to opposite ends of the pop spectrum.
5. Luke Bryan and Duck Dynasty's Willie Robertson, "Hairy Christmas"
The Duck Dynasty dudes didn't get to where they are today without a savvy business sense, and after dominating cable TV, releasing a Christmas album was just the next logical step. That doesn't make it any weirder to see a Louisiana duck-call magnate sharing the CMA Country Christmas stage with a guy who is, you know, an actual country singer. Still, "Hairy Christmas" deserves credit for being one of the few Christmas songs that bridges the gap between Santa-Christmas and Jesus-Christmas – after all, both guys had beards.
4. Lady Gaga and Joseph Gordon-Levitt, "Baby, It's Cold Outside"
Lady Gaga never met a tradition she didn't want to twist, spin or otherwise subvert, so why would the holidays be any different? For her 2013 Thanksgiving special, Mama Monster took the classic duet "Baby, It's Cold Outside" (which you may remember from Elf) and gender-flipped it, with Gaga herself playing the quasi-predatory seductress, and actor Joseph Gordon-Levitt as the innocent excuse-maker. It's weird on paper, but JGL's charm meshes well with his nice-guy role, and he and Gaga have plenty of chemistry to boot. This is probably the only song on this list that doubles as a statement against patriarchal gender roles.
3. John Travolta and Olivia Newton-John, "This Christmas"
It was the album no one asked for, an LP full of Christmas duets from an actor who hadn't sung in decades and his duet partner from a 35-year-old film. As a collection of songs, This Christmas is perfectly fine (although whatever technology is making John Travolta sound like he's still in his 20s needs to be beamed into our office, ASAP) – as a piece of Hollywood kitsch, it's priceless.
2. Bing Crosby and David Bowie, "Peace on Earth/Little Drummer Boy"
Most people hear about this 1977 duet a thousand times before they actually see it. Two artists, one a legend on his way out, the other in the process of becoming one. They talk for a few minutes, and it's not clear whether or not each knows who the other one is. Then they sing a song, only it's two songs, and they barely look at each other while doing it. All of this is wrong, and yet it's still so right: The lives of these two men should not be intersecting, but for a few minutes, they did. It's a Christmas miracle.
1. Justin Bieber and Busta Rhymes, "Drummer Boy"
Watch the title – the lack of "Little" is our first indication that Justin Bieber and Busta are going to be coloring way outside the lines on this one. Our next hint comes 45 seconds in, when Bieber abandons the song's traditional melody to start rapping. It's an oddly egotistical verse for a holiday song, crowing about the Bieb's legendary skills and implying that his flow belongs in the Bible, and it's made even more laughable by the tendentious moralizing in Bieber's second verse. ("It's about time for you to act merrily / It's about time for you to give to charity.") Sandwiched between them is a typically motormouthed Busta Rhymes verse, which deals with rhymes the way Buster Keaton dealt with trains.
Along the way, Bieber periodically returns to the original "Drummer Boy" lyrics, only this time he shoots the notes sky-high and rides them down on a shuttle of Mariah Carey melisma. The fact that an underage Canadian is duetting with a 39-year-old rapper is the least weird thing about this song, and that's what makes it so great.