(To the tune of “Boggis, Bunce, and Bean”)
DS9 s2e19 “Blood Oath” featuring returning TOS actors William Campbell (Koloth, s2e15 “The Trouble with Tribbles,” also played Trelane), Michael Ansara (Kang, s3e7 “Day of the Dove”), and John Colicos (Kor, s1e26 “Errand of Mercy”)
I meant those 3 didn’t have the ridges in TOS, but did in DS9. Its been a while since I watched any of those episodes but did they say that it’ll cure itself and Kor’s ridges naturally returned?
There is no official explanation for their change back in appearance between shows. Roddenberry’s position was to “imagine” the ridges were always there in TOS (make-up of the time being a constraint), but Worf in DS9 renders that point moot.
IIRC, there’s a line at the end of those episodes about the Klingons doctor working on restoring appearances. Guess they were at the back of the queue