5. 'Roanoke' (Season 6)
The gimmick of Season Six was that its theme wouldn't be revealed until the very first episode -- elliptical billboards and advertisements showed off a myriad of possible scenarios, with a logo that formed a stylized "6?". When the first episode finally aired, the show took on the form of a faux supernatural documentary, with two sets of actors playing each character (the real person and the performer reenacting the scenario on the documentary). But even then, the true format of the season changed when, halfway through, the fake documentary was over and a new one was presented, with the actors and the real people reconvening in a haunted house near where the Roanoke colony went missing.
The back half of "Roanoke" was way funnier and scarier than the first half (even if it was more conceptually chaotic), and it's a testament to the show's compulsively watchable nature that anybody stuck around through the extended experiment. It was also a shock to see Lady Gaga, the glamorous epicenter of the previous season, smeared in mud and portraying a barely recognizable wood witch. Hey, anything for the applause, right?