Just in time for Halloween, the Off-Off-Broadway troupe Bedlam is spicing up its presentation of Hedda Gabler with a Walpurgisnacht dance. That unexpected choreographic interpolation, with flashing lights, thump-y music, and Hellfire Club costumes, might strike the fancy of Sigmund Freud but would certainly surprise the play’s author, Henrik Ibsen—and perhaps also Jon Robin Baitz, whose adaptation, based on Anne-Charlotte Hanes Harvey’s translation, the production utilizes.