A new season of The Twilight Zone usually means, among other things, a new opening sequence. It was decided to contextualize the elements in Rod Serling's revised opening narration with actual objects (in order: door, window, eyeball, Einstein's Theory of Relativity, mannequin, clock). The whole thing would crescendo with the appearance of the series name, which had inexplicably become, simply, Twilight Zone (dropping the word The). Compared with the relative austerity of season 3's singular, spinning spiral, the new opening is positively bursting with diverse imagery.
This new opening sequence ran roughly five seconds longer than those of seasons two and three, so the existing theme music (Two library cues by Marius Constant, "Etrange No. 3" and "Milieu No. 1," spliced together) was now too short. The existing end theme ("Etrange No. 3" and "Milieu No. 2" spliced together) was re-edited to create the new opening theme; unfortunately, the result lacks the frenetic urgency of its predecessor.
Let's break it down, shall we?
You unlock this door with the key of imagination.
Beyond it is another dimension.
A dimension of sound.
A dimension of sight.
A dimension of mind.
You've moving through a land of both shadow and substance...
...of things and ideas.
You've just crossed over into...
...The Twilight Zone.
(dissolve to opening scene)
Here it is in full motion:
This opening sequence would carry forward into season 5, making it the most used --- and probably most recognizable --- of them all. It's my least favorite, truth be told... probably because I've seen it so many times.
The new opening sequence is only one of several major changes --- cosmetic and otherwise --- that season 4 will bring. Stay tuned.