[mrandish]

I'll add one other thought which just occurred to me: Most of the serious fans who like the "gimmick" episodes such as the musical and Lower Decks cross-over, like them because of the gimmick. Whether the specific reason is that it's so different, creative, fun, well-executed etc - it's still about the gimmick. While various gimmick episodes certainly have their fans, those episodes are not commonly found near the top of "Best Episodes Ever" lists.

Conversely, there are a quite a few creatively bold Trek episodes which branch significantly into different genres, yet don't go too far which are commonly found at the top of "Best Episode Ever" lists. For example, TOS episode "City on the Edge of Forever" is considered one of the greatest episodes of not just Trek but any sci-fi show - and it's a 1930s noir detective story! Yet when you read descriptions of it, it's not described as "that noir detective episode", it's more "the amazing Star Trek story Harlan Ellison wrote." It's not remembered for the gimmick, it's revered for the story. Similarly, TNG episode "Inner Light" is an adult drama that could easily be a non-sci-fi fantasy movie starring Tom Hanks - yet is ranked in the top five TNG episodes of all time. The key difference is they are great episodes with gimmicks, not episodes with great gimmicks.

[ndsipa_pomu]

I agree about the difference between "great episodes with gimmicks" and "episodes with great gimmicks" and I'd put the SNW musical episode into the latter - it was them having fun with the whole premise and probably shouldn't be considered canon.

Personally, I enjoy it when writers/producers try out an experiment and have particular episodes that don't really fit in with the themes and expectations of the series as a whole, but they do tend to polarise people.

The classic example that I think of with regards to musical episodes is the Buffy The Vampire Slayer epsiode "Once More, With Feeling". Joss Whedon had been experimenting with different concepts, such as "Hush" (the opposite of a musical episode) and "The Body" (stunning piece of television in my view), so throwing in a musical episode wasn't completely unexpected, but that particular episode pushed forwards and resolving some major plot points with characters revealing deep secrets.

(It's interesting that the three Buffy episodes I mentioned are considered the best episodes despite them having dramatically different styles).