What We Do In The Shadows boasts a simple, sketch-comedy premise: It’s a mockumentary about vampires. That’s a funny idea, but it’s not necessarily an idea funny enough to sustain a feature-length film. Indeed, directors Jemaine Clement (Flight Of The Conchords) and Taika Waititi (Eagle Vs. Shark, Boy) originally made Shadows as a short nearly a decade ago, before their respective careers had taken off. Happily, though, they’ve realized quickly something that many sitcoms take a while to figure out: If the characters are distinctly realized, the jokes will mostly take care of themselves. The result is more often amusing than gut-busting, but it doesn’t wear out its welcome, and that’s fairly impressive in itself.

In theory, the documentary crew in Shadows is filming preparations for an annual monster shindig, the Unholy Masquerade. But that’s really just the flimsiest possible excuse for a narrative in a movie devoted almost exclusively to petty bickering and other goofy juxtapositions of the supernatural and the mundane. The mock doc’s subjects are four undead roommates sharing a big, creepy New Zealand house; they range in age from 183 to around 8,000. Viago (Waititi), who was originally an 18th-century dandy, is the de facto leader of the group, or at least the one who’s in charge of the chore wheel tacked to the kitchen wall. There’s also Vladislav (Clement), who dates back to the Middle Ages and was renowned for his torture chamber; Deacon (Jonathan Brugh), a sort of slacker vampire; and the truly ancient Petyr (Ben Fransham), a dead ringer for Nosferatu. Complicating matters, Petyr “turns” one of their many victims, a regular guy named Nick (Cori Gonzalez-Macuer), who has considerable trouble adjusting to his new, uh, deathstyle.

Clement and Waititi—who met in college and subsequently formed a couple of comedy groups together—also wrote Shadows’ screenplay, and they have a lot of fun playing around with various aspects of vampire lore. Not casting a reflection in mirrors, for example, makes it impossible to check your hair or tell whether an outfit works; the inability to enter a building without being explicitly invited causes all kinds of problems when it comes to getting into discos and nightclubs. The movie is at its best, though, when it’s simply allowing these oddballs to bounce off of one another, as if they were ordinary roomies who just happen to have fangs. Waititi gives Viago an irrepressible puppy-dog enthusiasm that clashes beautifully with Clement’s quasi-sexy brooding as Vladislav (the latter looks surprisingly studly with long, unkempt hair and a Van Dyke beard), while Brugh functions much like Harry Shearer in This Is Spinal Tap—sort of like lukewarm water. Whenever things start to flag a bit, the boys toss in a feud with some oddly polite werewolves (“werewolves, not swearwolves”), or shift focus to the hapless humans in the vampires’ orbit, notably Nick’s best mate Stu (Stuart Rutherford, magnificently bland). If What We Do In The Shadows often plays more like a TV pilot than a movie, at least it’d be kicking off a pretty damn good show.