John C. Reilly is ready to sink his teeth into the lead vampire role in “Cirque du Freak,” for Universal.Paul Weitz wrote and will direct the adaptation of the bestselling children’s series by Darren Shan. Weitz will also produce with Lauren Shuler Donner. Production begins in February. Reilly, who next opens in “Walk Hard: The Dewey Cox Story,” will play a vampire who drafts a 14-year old to serve as his assistant. The youth is turned into a half-vampire and becomes the catalyst in a battle between vampires and the rival Vampanese. Studio bought rights in 2005 to a series of 12 books. Reilly stars in “Walk Hard,” which will be released Dec. 21 by Columbia Pictures.