most of my headcanons for vocal synth characters tend to be based on inside jokes or something i experienced that i find funny, as well as the more comedic ones inspired by semi-canon information or common headcanons used in a more serious manner turned up to 11 for comedy.
one of my more recent ones for meiko is that she's completely horrible with specific dates (mostly birthdays), because of a moment that happened while i was playing project diva f2nd, in the diva room while grinding out item events. the quiz item had luka ask the question akin to "when is meiko's birthday" to kaito and meiko herself. with meiko being the person who got it wrong. another one is taking miku's inital "android from the future" concept and making her, the kagamine's, and luka all time-travelers from the future. and making luka know english and debut after the other three because she got sent to britian instead of sapparo. and her picking up more distinctly uk mannerisims + being genuinely supprised when the sky's blue.
i also have a variety of headcanon's for different au's and portrayals alike. one of my au's main kaito's has a bad tendency to spend all his pocket money on impulse, while another kaito from a different au gets scammed out of his money easily. the connecting "kaito is bad with money" headcanon can be portrayed in a variety of ways. and thats sort of beautiful.
