Elvira’s staging a threesome of fearsome: with publisher Huge Heftee, in “Frightening Development!” by Strom, Smith, and Vey; with celebrity nuptials, in “The Wedding Hammer” conclusion, by Hetherington, Cool, and Rubinstein; and with those cute “Larry Plotter” kids, in “Favor of the Month!” courtesy of Miraglia, Howell, and Marie Severin.