Often touted
as the worst episode of "Star Trek" ever filmed.
Gene L.
Coon wrote this episode under his penname "Lee Cronin."
(Probably a good idea.)
The bridge
viewscreen in this episode had been equipped with a rear-projector,
comparable to the viewscreen used in "The Menagerie."
As a result, director Marc Daniels filmed the scene where Kirk,
Sulu and Chekov attempt to trace the path of the alien ship with
all three actors standing in front of the viewscreen with the actual
display, rather than a blue screen effect.
Chekov heats a rock with
his phaser without melting the snow right next to it.
When Kirk and the crew
reach the underground city, he stuns Kara and removes the bracelet
from her arm. After he removes it, the unconcious Kara quite deliberately
lays her hand flat on the ground.
The shots
of the crew falling unconscious were later used, unaltered, in
"The
Way to Eden", complete with Nurse Chapel taking her extended
fall in sick-bay. How coincidental that the same shot is used in
two of the worst episodes.