As “Dead Mouse Productions,” Gary Smart and Christopher Griffiths have been making horror documentaries for a decade.  You may have seen their comprehensive retrospectives “You’re So Cool, Brewster: The Story of Fright Night,” “Leviathan: The Story of Hellraiser and Hellraiser II” or their recent “Pennywise: The Story of It.”  Dead Mouse’s latest doc, “Hollywood Dreams & Nightmares: The Robert Englund Story,” is a slight change of pace that focuses on the career of one actor.  Smart and Griffiths sat down to discuss their latest film, how documentary filmmaking has changed since they started, and the “Zelig”-like career of the iconic Robert Englund.