It must have been touted that week as a must-see programme by TV guides, or something.

Hmm, for me it was a pure accident. At its first broadcasting it wasn't pitched as “the greast TV hour” hour yet. But it still presents an interesting problem – it is one of the best episodes, but it is absolutely unrepresentative of the series as the whole – not in terms of quality, of course. So what is best episode to begin watching with? I don't know. Intervention worked for me.