If you're interested in this kind of thing you might also want to check out the book "The Nit-Picker's Guide For Classic Trekkers" by Phil Farrand if you can find a copy. (It's pretty rare these days.) It's mainly a guide to all the various errors in the classic episodes of Trek. And by errors, I mean mostly plotholes, leaps in logic, continuity errors, etc., leaving out the obvious things like fake looking sets or aliens, etc. There's also little essays on things like recurring themes in the Original Series, quizzes, and other things like that. Again, if you're interested and you can find it, it's worth a read.