Also, you can tell they're not really kissing. It's actually pretty unconvincing.
Yep. They just touch lower lips. You can plainly see Shatner's open mouth below his upper lip. So when I read about how Shatner "snuck in the kiss", just in time where they couldn't do another take, I was like "what kiss?"
I think it was in Shatner's "Star Trek Memories" and it struck me as one of the few stories to feel actually true; something about they shot it multiple times there was a choice of going with an actual kiss or a fake one. They "copped out" went with the fake one and he said "when you watch the episode next time, you'll see it."
The book is in my attic somewhere, so I can't dig it out at the moment....