A Series Of Unfortunate Events Season 2: 10 Miserable Fan Theories You Don't Want To See
5. Some Of The Adults Are Immortal
This is one of the more out-there ASoUE fan theories, and largely predates the TV show (though it does still largely apply), and it's the idea that a lot of the adults we meet - and in particular Lemony Snicket himself - are actually immortal.
Ok, yes, it's kinda crazy, bordering on vexingly formed delusions, but there is textual evidence to at least support the claim. Mostly it stems from the hints that Snicket knew a number of historical figures, such as William Shakespeare (died 1616), William Congreve (died 1729) and C.M. Kornbluth (died 1958). The writer goes on to allude to various other events from across the books, which adds up to an oddly compelling (if rather insane) case.
If you move that to the show, which isn't really a stretch at all save for the fact we haven't (yet) had the same references, then the theory applies just as much as it does to the books. And given the anachronistic setting of the series, the fact that the adults have all known each other for a very long time, and that somehow people manage to survive against the odds (well, not everyone), who knows... (Yeah, it almost certainly isn't true, but it's nonetheless fun to think about and there is text to give it some basis.)