Co-writers-directors-stars Taika Waititi and Jemaine Clement lovingly impale bloodsucker mythology with the sharpened wooden stick of comedy in their delightfully silly vampire mockumentary, "What We Do in the Shadows" (unrated, Paramount). Their satire is a crude but effective tool. Clement is half of the comedic folk-music duo Flight of the Conchords. Fellow New Zealander Waititi is behind the celebrated indie comedies "Eagle vs. Shark" and "Boy." This new movie is set in a Wellington group house, where four undead housemates — ranging in age from 183 to 8,000 — are being followed by a film crew. The jokes are sometimes lowbrow, but often very funny.