There are lots of bad movies, heaven knows. But Tommy Wiseau’s “The Room” was bad in such a strange and singular way, inspiring as much fascination as derision since its release in 2003. Who was this menacing-looking, stringy-haired auteur with the untraceable accent, and why did he finance, write, direct and star in his own inept erotic drama?

James Franco’s hilarious and surprisingly sweet “The Disaster Artist” attempts to answer those questions. The film opens with a montage of actors and directors (Kevin Smith, J.J. Abrams, Kristen Bell) attesting to their fascination with “The Room.” Actor Adam Scott says he would love to take a time machine and visit the set of “The Room” as it was being created. “Disaster Artist” is the next best thing.

“Disaster Artist” is based on the memoir of the same name by Wiseau’s friend and co-star, Greg Sistero. As played by Franco’s brother, Dave, Greg is a handsome, middling actor in San Francisco, too self-conscious to really put himself out there in acting class. He’s drawn to another student in the class, Wiseau (James Franco), a man of mystery who flings himself full-tilt into every performance.

Franco’s impersonation of Wiseau — the heavy-lidded eyes, the soft laugh, the sudden bursts of anger — is pitch perfect. But he’s able to go deeper into Wiseau’s character than Wiseau himself ever could, creating a figure on the margins of show business that’s both a little unnerving and kind of sad. The fact that we don’t know anything about his past makes him more interesting. He seems like a space alien sent to live among humans, picking up bits of American slang and parroting them back.

The screenplay by Scott Neustadter and Michael H. Weber (“The Spectacular Now”) wisely grounds the movie in Greg and Tommy’s friendship, as the two struggling actors pump each other with a shared delusion of making it big in Hollywood. Wiseau, who is repeatedly told by casting agents and acting coaches that he should try playing villains, instead dreams of himself as a James Dean-like leading man. (Ironic, since Franco played Dean in a TV movie early in his career).

But the film cannily shows that the marginally talented Sistero’s dreams are almost as delusional. Hollywood chews out and spits out pretty boys like him every day. At least when Wiseau walks out of a casting room, he’s remembered.

He also seems to have an inexhaustible cash flow coming from somewhere (he won’t say where), enough that he decides he’ll make his own movie. The second half of “The Disaster Artist” focuses on the troubled production. Filming goes way over budget (“Day 52 of 40” reads one subtitle) and Wiseau spins out of control, to the horror of the professional crew members on set (including longtime Franco partner Seth Rogen). “The best thing anyone can say about this is that nobody will ever see it,” one crew member muses in a bit of comic foreshadowing.

For fans of the film, which now has a cult status to rival "Rocky Horror Picture Show," seeing some of the film’s most notorious scenes and characters recreated with slavish devotion is very funny. Some of the casting choices are so perfect they draw immediate laughs, like Josh Hutcherson as floppy-haired man-child Denny.

I wouldn’t say it’s essential to watch “The Room” to enjoy these scenes — I wouldn’t force that on anyone — but checking out a few YouTube clips ahead of time might enhance the experience. If you want the full experience, the Majestic Theatre, which doesn't miss a trick, is screening "The Room" as a "Brew 'n' View" on Dec. 30.

What should be a Hollywood cautionary tale somehow becomes an unlikely cult success story; faced with derision and waves of laughter from audiences, Wiseau now claims “The Room” was meant to be a comedy all along. He and Sistero still tour with it to adoring fans. In a way, Wiseau was a visionary — not of Hollywood movies, but of internet viral videos, where the line between being in on the joke and being the joke is often invisible.

Like Tim Burton’s “Ed Wood,” “The Room” is both a movie that pokes fun at its subject and celebrates it, with an odd but strangely inspiring message: Do what you love. Even if you’re terrible at it.