The annual weekend Twilight Zone marathon continues, and Syfy has saved a lot of the best for last. At 4:30 p.m. ET today, Agnes Moorehead, in an almost completely silent episode, plays a farm woman taking on tiny aliens in “The Invaders” (seen left, above). An episode we always show in our introductory Rowan University TV History & Appreciation class, “The Monsters Are Due on Maple Street,” is shown at 10 p.m. ET, followed at 10:30 p.m. ET by that classic episode of kitchen nightmares, “To Serve Man” (seen left, below). Finally, at 11:30 p.m. ET, there’s “Nightmare at 20,000 Feet,” in which William Shatner encounters airline problems even more disturbing than charging for luggage or in-flight meals.