Have you ever known two wildly different people who have begun dating, even though all logic and social norms points at this being a recipe for disaster? This couple appears so ridiculously mismatched that you're forced to believe they got together JUST to mess with you? Well, every once in a while, a song featuring two musicians that are basically from different planets hits the charts and garners a very similar reaction from listeners. Its not unusual for a pair of musicians--or even a gaggle, if this happens to be a Lady Marmalade type of situation--to test their chemistry by writing a song together. Whats surprising is just how many of those duos come from completely different backgrounds and genres, with almost no common musical DNA. And even more surprising is how many of those ridiculously conceived collaborations go on to become iconic pieces of pop culture history. Rappers and rock stars, guitarists and DJs, wistful crooners and angry growlers: eventually, they end up in the same room together and get the idea to put a record together. Over time, the results have been middling to horrifying. But the law of averages suggests that sometimes, against all odds, a few of these oddball combinations will actually turn into something magnificent. Here are the artists who defied all sense of logic and said, "To hell with it. Let's spend some time together."