Do you really think people beat impossible? While possible (though not probable by any means) that someone has beaten it, wouldn't there be at least some DOCUMENTATION of it? As far as I know, a Google search has brought up nothing (although it has brought up a Youtube video of a 4 boss run on impossible, posted on the 18th of November, impressively enough).
Either way, I WANT to beat it, but I am pretty sure I lack the patience or willpower to actually succeed at the task. So far, on the upper path, I'm CONSISTENTLY getting to and through Tyson (a good start, I suppose), but the Ghouls 'n Ghosts section keeps tripping me up due to MY STUPIDITY (IE: Link stabbing me, moving spikes were the MAJOR ones, but I've gone so far in my failure as to jump RIGHT into the spikes at the moving platforms on the 2nd screen before Mecha Birdo... heck, I even allowed a ZOMBIE to kill me once!).
My ventures on the left path have ended in mostly bloodshed. I'm consistent up to immediately after Tetris. For some reason, I always choke up when dealing with the moving spike wall. However, on one attempt, I did manage to get to Kraidgief and killed him with the glitch (unintentionally, I didn't realize K, which was my jump button, was the trigger. I don't intend to kill him with the glitch in a successful run). On this same run I managed to get to and through the Koopa Clown Car (at first, I was going to go to Mother Brain, but then I realized that the post-KCC section was more brutal than the post-MB section, so I went that way first, hoping to get the harder part out of the way). Of course, I failed instantaneously on the spiked ceiling room immediately after the KCC. Oh well... back to the drawing board.