This episode is memorable because it takes all of the traditional spooky-house cliches and, while serving them up one after another, takes an almost joking look at them. The honeymooners seem to expect everyone of them before crop up, which definitely makes the storyline more interesting than if it were played "straight" (i.e., if they had no idea that the people in the house would be so creepy, etc.).
A lot of this episode's success lies in the casting of Elizabeth Montgomery (Bewitched) and Tom Poston (Newhart, also Mr. Looney from Family Matters) as the leads. Their comedic skills help this episode achieve the desired tongue-in-cheek effect. At the same time, they are suitably nervous so that the entire episode doesn't deteriorate into an hour-long joke. They hit the perfect balance: One or the other always seems to know which cliche is coming up next, but they still manage to be somewhat creeped out since they are definitely not in control of the situation. Veteran horror actor John Carradine also gives a strong performance as the house's owner.
The other component is the twist ending, which I won't spoil for you here. Suffice it to say that you know from the beginning that something is coming, and you have fun trying to guess what it will be. It can be figured out before the twist comes, but not too early. I haven't seen every Thriller episode yet, but so far, this is my favorite. A series classic.