The annoying part is it really only needs a handful of things to be saved.

A binary flag for each pick-up and boss defeated isn't really that big a deal, for 20 options it's a little over a million options, you could easily store it in a 7 digit number.

Using hexadecimal you could store it in 5 characters(0-9,A-F = 16 options). If they used hex it'd be really obvious what each character was and a checksum would still only make passwords 6 or 7 characters.

The weirdest ones were the ones that used bizarre graphics and long passwords, because making a note of multiple lines of "armour heart heart sword heart armour sword face armour" is just ridiculous.