I was thinking about this before the Tholian wave, but it’s apropos.
It unscientifically appears to me that TOS had a far higher incidence on non-humanoid aliens than later series. Tholiens, Horta, the flying neural parasites on Deneva; while there were many bipedal aliens sometimes differing only by skins color, many were non-bipeds or were bipedal but radically different from humans, like the Gorn and the salt vampire. In later series, it seems nearly all aliens were reduced to bumpy head species.
TOS ran for only three seasons, and truly different aliens are expensive; I understand the economics of going the prosthetic forehead route. And it’s difficult to have recurring truly alien biology in a series.
My question is whether anyone’s done a statistical analysis covering the originality of aliens, per series, based on divergence from the humanoid base. Does it only seem like TOS had more different types of aliens (intelligent and non) because it was so short, or was the universe really more diverse in TOS?
That actually was something that irked me about TNG at the time and it still annoys me a little. TNG never had Andorians (not counting one holodeck projection) or Tellarites. They occasionally had non-human aliens, but most of the time it was the forehead prosthetic of the week. And I really didn’t care for the explanation in The Chase because it’s essentially saying that all the humanoids are special but all of those other non-humanoid aliens can get fucked because apparently not a single non-human entity, let alone the old intelligent gas cloud standby, were around when The Chase aliens were.
Well that, and the whole idea of the secret message DNA puzzle was dumb.