2. Carbon Creek (Enterprise)
Plot in Two Lines: Vulcans ended up on Earth before that First Contact moment with Zephram Cochrane. Serious. They did.
Why Your Trek Friend Says It's Good: Enterprise drops in on Earth and mixes it all up in the 20th Century. It's one of the more unusual moments in Enterprise and takes a very unusual tack where the main cast and the ship take a massive backseat. It also demonstrated that the show could spread its wings and do some different things. It wasn't reliant on the spacebourne format. Seeing Vulcans on Earth before the Big Day is pretty cool as they try and fit in, invent velcro and really coming to terms with the Human Condition that Star Trek was originally built on exploring.
Why It's Not Actually That Good: Another one of those moments when Enterprise decided to give the franchise history a bit of a kick and mess things up (see also Regeneration with the Borg). Why there needs to be these tinkering episodes defies logic and even suggests that the engine was finally starting to run out of steam by this point. They also did that western one, North Star and another one in the present day, Carpenter Street. Was this Enterprise's occasional gimmick? To add insult to injury there's the "suggestion" by T'Pol that it's all a story and might not have happened (or did it?!). Hang on - the Vulcans invented velcro?! Come on...please....