The appreciation of so-bad-it's-good cinema is not new. As Village Voice critic J. Hoberman noted in his seminal essay "Bad Movies," "The Surrealists loved bad movies, seeing them as subversive attacks on the tyranny of narrative form." And as the great critic Pauline Kael wrote in "Trash, Art, and the Movies" in 1969, "Movies are so rarely great art that if we cannot appreciate great trash we have very little reason to be interested in them." However, it was the publication of Michael and Harry Medved's book The Fifty Worst Movies of All Time that helped to usher in a new, codified fondness for cinematic ineptitude; a few years later, the institution of the annual Golden Raspberry Awards and the popularity of Mystery Science Theater 3000 brought ironic movie appreciation to the mainstream.

However, in the ensuing years, it's become increasingly difficult to determine that certain je ne sais quoi that distinguishes a merely mediocre film from a sublimely bad one. Hollywood churns out plenty of laugh-free comedies and unexciting action flicks each year, but many are made with at least a semblance of proficiency and feature competent actors. Lapses in craft don't necessarily make for bad movies, either; the many supporters of the film noir classic Detour (100 percent) will concede that it is riddled with technical imperfections. Intentions are important, too: films with camp followings, like Road House (30 percent) and R. Kelly's Trapped in the Closet may be loaded with absurd dialogue and overheated plotting, but it's pretty clear that's what their makers were going for. And for every perversely hilarious folly like Valley of the Dolls (36 percent), there are theoretical so-bad-they're-good entries (From Justin to Kelly, nine percent, or Myra Breckinridge, 26 percent) that are, in reality, pretty much unwatchable. (Frankly, I'd be surprised if RT's worst-reviewed film of all time, Ballistic: Ecks Vs. Sever, has any ironic defenders.)

What makes for a truly stellar so-bad-it's-good movie is a gulf between conception and execution so wide it helps audiences to reconsider the notions of what constitutes good filmmaking. No essay on bad movies is complete without mention of Edward D. Wood, Jr., the master of delirious cinematic wrong-headedness. So enamored was Wood with the process of directing (and so tight were his budgets), that he would rarely, if ever, reshoot a scene. Utilizing every cut-rate trick in the book (hubcaps stood in for flying saucers, stock footage abounds), Wood crafted a series of anti-masterworks that brought to light his obsessions; Glen or Glenda? (33 percent) was a plea for the tolerance of transvestites (of which Wood was an enthusiast), and Bride of the Monster (29 percent), the last speaking role of Bela Lugosi, whom the director considered to be a great star, even years after his prime. Wood's films were so weird and so seemingly incompetent they stayed well below Hollywood's radar during his lifetime.

But a funny thing happened on the way to obscurity and posthumous derision. Slowly but surely, Wood's films were absorbed into the cinematic cannon, not because of their quality but because of their singularity: nobody made bad movies like these. Hoberman has called Wood an unconscious avant-gardist, and he's something of a patron saint for against-all-odds indie filmmakers. (Tim Burton's brilliant, Oscar-winning biopic didn't hurt matters, either.) Wood's most famous work, Plan Nine From Outer Space (60 percent!), was long considered the worst movie ever made. But how bad is it, really, more people today have seen it than, say, How Green Was My Valley? Featuring an all-star ensemble of Wood regulars (including former wrestler Tor Johnson, ghoul girl Vampira, and charisma-free narrator Criswell), Plan 9 tells the story of aliens who want to reanimate the dead into an army that will conquer the world. After shooting only three minutes with Lugosi before his death, Wood hired a chiropractor friend to flesh out the role (which he did -- by covering his face with his cape). The mistakes are too numerous to count: characters call each other by their real names, daytime and nighttime scenes butt against each other (sometimes in alternating shots), cardboard tombstones shake in the graveyard scenes, and the fight sequences are some of the stiffest ever captured on film. But Plan 9's badness is so pervasive and so original that contemporary critics find it -- gasp! -- pretty impressive. "Like the greatest cinema poets, [Wood] always managed to work in his own particular pet pleasures or concerns, and that odd, ear-bending dialogue is almost like a bizarre kind of open-verse poetry," wrote Jeffrey M. Anderson of Combustable Celluloid.