Sarek is probably the most important crossover episode in the Star Trek franchise, because this episode allowed The Next Generation to acknowledge the events of The Original Series properly for the first time. The character of Sarek himself was fairly low key in The Original Series, only appearing in Journey To Babel. But his appearances in the film franchise boosted his notability so that an episode of The Next Generation could be built around him. As for the episode itself, it is good one. Sarek appears in a credible manner. Even with his appearance, the most important point came towards the end of the episode. The writers and producers apparently went back and forth on a single word in the script for days until they finally agreed that they could include it. This one word changed the way in which TNG approached crossover episodes it was during the mind meld between Sarek and Captain Picard, when Picard suddenly yells out as a result of Sarek's conflicted emotions; "SPOCK!" After that word was spoken, the unwritten rule was broken and TNG could start to consider crossovers properly. If it wasn't for Sarek, we wouldn't have ever had Unification and not just because of the plot setup but because the producers became more open to it.
