The parts where the clown appears to both the youngsters and adults is quite terrifying and scary.
Also the finall chase to kill the thing. After it is supposedly killed the evil laugh sparks the question can this evil entity be killed at all?
Other great horror miniseries were Salem's Lot and The Dark Secret Of Harvest Home with Bette davis.
The Dark Night Of The Scarecrow and Crowhaven Farm were great TV horror movies as well.
Regarding Sci Fi, V The Miniseries & V: The Final Battle were excellent. Super special effects using just the right amount of computer animation. Today they use too much.
