
So just what is that strange bald patch in a part of the head that even in Bill Shatner's case, is likely still covered with his own real hair?

We simply don't know...
Now, finally some more general analysis of the "Denny Crane look":
William Shatner, we believe, ended his "TJ Curly" weave or hairpiece use between 19th July and 7th September 2000. Incidentally, this is the same time that he began seriously seeing what was to become his fourth wife Liz. A connection? Very likely. After the tragic death of his third wife Nerine a year earlier, perhaps a new hairstyle to impress a new girlfriend (and we don't mean that frivolously in any way) seemed like the logical choice - a way to spruce up to impress a new lady. And why not?
Bill Shatner with his future wife Liz in early September 2000,
following what was likely an expensive hair transplant.
To see more on how we came upon the above dates, look at the middle of the page in the Getty Image sequence here.
UPDATE: A reader asks, if the above is the case, then how come Shats appeared to return to the toup during 2006 (and possibly in a few other instances too)?

Disclaimer: we have uploaded two watermarked Getty Images in this post - we're uncertain if the company's watermarked images are freely available or not. Nonetheless, if Getty asks us to take them down, we will certainly do so.