"It's a Good Life" is one of the four or five Twilight Zone episodes that is familiar through popular culture, even to many people who have never watched the show. Based on a short story by Jerome Bixby, rewritten by Rod Serling, and starring Bill Mumy in his breakout role as Anthony Fremont, as well as Cloris Leachman as his mother.
This episode starts in a different way than most Twilight Zone episodes, with Serling explaining the locale and premise before the first scene, rather than after it. We are then dropped into what is just an average day in the life of a small town in Ohio that happens to be run by a demonic six year old.
There are a number of Twilight Zone episodes that succeed despite a premise that could have been silly. This is one of them: it is never explained why Anthony is so powerful, or why he is so evil. Much of the credit goes to Mumy, who managed to mix realistically childish behavior with the menacing presence needed for the role. Very little of Anthony's actual power is shown, which is probably a good decision: special effects were never The Twilight Zone's strong point. The episode instead focuses on the reactions of the people around Anthony, and the slavish devotion they show to his whims.
The secret to the episode's success, at least to me, is that it focuses not on the frightening, but on the creepy. Much as with Mumy's earlier episode, Long Distance Call, there is an unsettling Freudian element in the story. The role reversal of having adults focused on pleasing a child is scary in a way that the (unshown) three-headed gopher could never be. The episode is awkward to watch at times, and communicates totally the walking on eggshells feeling of being in a home where someone has managed to become a petty tyrant. The usage of supernatural powers is just a way to frame that, and the episode in the end suggests that (as is so often the case) the only thing to fear is fear itself.
This is one of the many Twilight Zone episodes that lives up to its reputation.