As a midsized venue, Lakeview’s Mercury Theater has been quite successful in presenting musicals with complex and unusual special effects, costuming and characters.Of particular note were “Avenue Q” with its raucous puppets, “Little House of Horrors” with flesh-eating plant Audrey and “Barnum” with its death-defying circus acts.Its current production is “Spamalot,” the outrageous take on the Monty Python sketch comedy …