m!ISTJ and n!ESTJ. So I have no idea if the whole community around redesigning the 16P avatars and giving them elaborate backstories and lore is as active on Tumblr as it is on Instagram but from what I've seen I'm guessing it's not. Unfortunate. I miss the Instagram MBTI community from 2021/early 2022.
Super brief backstory that in no way adequately explains anything time: both of them are residents of a giant space station-esque scientific compound, and were best friends and coworkers. n!ESTJ is the head of structural security for the entire compound, which involves managing a team of support/repair robots. m!ISTJ was a scientist who died in an explosion (not going into detail on that because there's a lot), but had a backup of his consciousness stored from a prior experiment. For several years, he was thought to be completely gone, until he was rediscovered when his son (m!INTP) accidentally transferred the backup from an old computer from his home into one of the robots that was undergoing repairs. Cue tearful reunion and shared existential crisis. Anyways now they are working together again and building m!ISTJ a better body so he doesn't have to stay in the tech support robot. (This is possible in this universe, n!ENTP is another character in this branch of the story that has a robot body but again I will not go into that here.)
I do not know why I decided to create a whole universe based around a set of polygons from a fake MBTI website. The lore goes much deeper (aside from the space scientific compound, there's the planet it orbits with multiple civilizations and magic-adjacent energy that comes from its core and also n!ENFJ is just straight up an alien). I envy the amount of free time 2022 me had.