We know that R. Kelly teaming up with Britney Spears on a remix is liable to make a lot of people lose their shit, especially when that song is "Till the World Ends," the best single of the Femme Fatale cycle to date. But we also know that it's easy to download a mp3, paste some other guy on it, release it to the Internet and pass it off as real. It's happened to Kanye West, Mary J. Blige and god knows who else just in the last month. Yes, we were fooled both times. Yes, we're a little sore about it.

So, lacking proof, we think this "Till The World Ends" is one of those unofficial mashups. Listen to the tagged version, then read on to find out why we don't think this is real. (Prove us wrong! Or prove us right!)

Signs this isn't an official remix:

- This is "Till The World Ends," whose window for remixes was roughly two months ago thanks to new single "I Wanna Go." This is the "Till the World Ends" watch sale stage, not the remix stage.

- Britney's still singing "sicker than the remix," which means the track is sicker than itself. On the Nicki/Ke$ha remix, they changed this part.

- Other than R. Kelly's bit, where the backing sounds like a direct Audacity paste, the track is unchanged. Again, the Nicki/Ke$ha version changed itself up.

- R. Kelly is Twitter silent about it. Granted, he's been Twitter silent since June 17, at which point he was "touching everybody everywhere" with his music in a probably ill-advised turn of phrase. But we can't find an announcement anywhere else. Everything says this "surfaced," or "leaked," which basically means it washed up like kelp on people's Google Reader or YouTube. Meanwhile, Britney or whoever tweets for her is also silent about this when she's had time to thank every ninth fan who attended her concert. In Winnipeg.

- There have been about five dozen songs in the past year about partying/dancing/screwing until the world ends, including current No. 1 "Give Me Everything." It's more than plausible R. Kelly just had some apocalyptica lying around on a hard drive someplace.

Granted, two pieces of evidence do suggest this is real: R. Kelly's singing with Britney on "keep on dancing till the world ends" and the fact that he worked on In the Zone. Perhaps he, and not some fan/leaker, did the sloppy mashing-up! And either way, it's still "real" in the sense that you can download it and listen to it and dance to it until the next Rapture scare. But is it so much to ask to get warnings about these things? Even Ke$ha can take a drinking break to tweet about her collaborations!