2. “The Cage”
I know, I know…Right now you might be asking, “But wasn’t that the first-ever episode of Star Trek?” and while that is technically true, I also have to point out that “The Cage” did not make Star Trek a series. The second pilot, “Where No Man Has Gone Before,” did that. Despite interesting concepts, “The Cage” is a bit tedious and required significant reworking before Star Trek took the form we know.
While there are certainly aspects of the pacing and production design that make “The Cage” different from the majority of TOS, the bigger issue is that it is a fundamentally different show. There is no Captain Kirk, no Dr. McCoy, and really none of the other characters from TOS, except for an early incarnation of Mr. Spock.
Honestly, “The Cage” is better to watch when getting into Star Trek: Strange New Worlds at this point, rather than TOS. While Jeffrey Hunter’s Captain Pike is different from Anson Mount’s, they are still more similar to each other than they are to Captain Kirk. If you’re trying to get into TOS, You really should watch episodes that feature James T. Kirk, not Christopher Pike.