Its not a theory itself, but lore like a "this would be very interesting" so the non theory is
What if everyone avatar in the circus is based on with what they played the most while they were young?
Think about it: kinger maybe was a smart kid (or teached by his family, maybe his father and that would explain part of his father figure at the circus)
Queenie: the same with kinger but also this could add a bit more of implied lore: they probably meet during a chess match at a campus on university
Ragatha: a girl like ragatha probably had plenty of toys, but most of them probably dolls that were a gift from her aunts, or her mother gave dolls to her to "teach her to be a woman" or something
Jax: probably had or bunny plushes or yad a bunny pet, maybe Jax first contact with experimenting "femenine" things (bunnys are cute as hell, nothing to do with roles)
Gangle: probably gangle liked to act to her parents but once she tried to act in front of others in kindergarten she was too shy, the kids too mean and she slowly morphed her act expresion to draw expresion
Zooble: we know zooble had a job as a tattoo artist, bartender, so zooble abstract body surely is because zooble always played with free toys (like lego, dough, different kinds of combinable things, leaving zooble mind to grow expresive)
Pomni: uh... I dont know? I never seen jester toys... She played lots of balatro or something like that
Or well, if we want to be more free with the theory: pomni played a lot with her mind, with others too, surely she was like "ok, now im the dragon and you two are the knights" making her a jester, entertaining others, she grew with that until kids started saying she's too inmature and childish to keep playing like that
For the other abstracted ones:
Scratch would be my favorite: he played a lot with his doggy
Ribbit: played a lot in the mud, rain and things like that
Kaufmo: uhh... Probably liked to do pranks (based on clowns, once he grew he didnt made new ones, often grown people see most clown pranks like bad jokes)
I we want to think one for caine too: caine when created only had two functions, consume and create: mouth can consume, eyes too cause they consume the info by looking at it, caine being a digital thing if he speaks he creates, his voice is code so
Consumes with eyes and creates with voice