I'm glad they did nothing so pedantic as explaining the discrepancies of staging and makeup, playing them instead as an inside joke.
Worf's head should've simply - and abruptly - appeared as 1960's Klingon style, when he was in TOS' era and nobody would've noticed, or said something. At the same time, giving Michael Dorn a break, for a couple days.
Watching this episode again right now. I love it. My heart goes out to the understandably humourless Temporal Investigations guys. "I'm a doctor, not an historian!" Dax in the classic Sixties dress! O'Brien and Bashir in the elevator!