Continuity mistake: Why does Kirk think a being of pure energy is "impossible?" They've encountered several such creatures in the past in "Metamorphosis," "Obsession," and "Wolf in The Fold."
Visible crew/equipment: When Scotty joins Thalassa while she's working, she asks if he has "prepared the megaton hydrocoils," and the shadow of the boom mic can be seen moving at the top of the screen. (00:33:20)
Answer: After causing Norman to overload, all of the other androids shut down. The same could be said for the androids on the Enterprise.