@FandomChats Crack ships and rare pairs can often cross paths, but as I understand crack ships are pairs of characters that come from unrelated media. A crack ship can be rare of course, but isn't always, and a rare pair is not a crack ship since it just refers to ships from a piece of media that don't get a lot of attention.

I don't really seek crack ships but the honest enthusiasm of their fans can end up luring me in, and I have a couple crack ships I've fallen for hard enough to make my own fan art that I know have thousands (yes plural) of fan works, even going as far as to appear in top polls of popular fan work platforms and have IRL fandom events dedicated to celebrating them. Popular crack ships are IMO the most satisfying way of winning fandom lottery, a treat so unlikely to exist and yet so well-indulged, that's great.

I love a lot of pairs considered rare, though what's rare depends on where you're hanging. I have ships with only one or two fics on AO3 that have hundreds of works in non-English spaces. But... A hundred works seems to be considered rare in EN fandom anyway. I even see people say a thousand fics on an AO3 ship tag is "nothing". Newer fandom mindset is insatiable!