What We Do in the Shadows Jemaine Clement, Taika Waititi, Jonathan Brugh. Directed by Jemaine Clement and Taika Waititi. Not rated. Opens Friday.

If you ever wondered what Jemaine and Bret from Flight of the Conchords would be like if they were vampires, you can get half your answer from What We Do in the Shadows, a mockumentary starring and co-written and co-directed by the Conchords’ Jemaine Clement that often plays like "Flight of the Vampire Conchords." Taika Waititi, who wrote and/or directed several episodes of the Conchords’ HBO series, is Clement’s co-writer, co-director and co-star on Shadows, and the duo brings a familiar understated, deadpan humor to the story of three vampires who live together in a rundown house in Wellington, New Zealand.

The juxtaposition of the supernatural and the mundane is the movie’s primary source of humor, and for the first half-hour or so, that’s more than enough. But Clement and Waititi exhaust a lot of the potential of their one-joke premise fairly quickly, and the movie gets bogged down with far more plot than is necessary for what is essentially an extended comedy sketch. Still, the performances are all strong, and the filmmakers make effective use of the mockumentary format. Even when the laughs are less frequent, they continue through to the end, with plenty of quotable lines that fans will no doubt add to their Conchords repertoire as soon as they leave the theater.