fingerprints are not genetic, but are formed by the movement of the fetus in the womb. while they are not a reliable way to identify someone out of a general population (the likeness is about 1:10000; there have been wrongful convictions based off of fingerprint data) they can be used to differentiate two individuals.
almost everyone has some insignificant scarring on the hands or face that’s created after birth and which is tied to some stupid story about cutting cheese or whatever.
everyone has some weird fetish. if you don’t think your fetish is weird, it’s because you’re in company that shares it.
i found them interesting before i knew the tricks. i’ve still never solved one, because memorizing patterns isn’t interesting for a puzzle.