Theories about Jungs archetypes as they relate to Madotsuki.
The Shadow:
The dark sides of personality that we deny ourselves and project onto others. This could be Poniko/Uboa and/or the Toriningen, possibly even the Demon in FC World? It could even be, FACE, KyuKyu or the various vast wilderness dreamscapes.
In a more abstract sense, the Alley Demon, the Knife Effect , various monsters and even the Witch effect could be Madotsuki's shadow.
The Toriningen/Poniko really reflect this the most obviously, though.
The Animus:
Males meet the "Anima" or female/fem qualities, and females meet their "animus", which is likewise the male sorts. This could be Masada and/or the Demon, since they are most often portrayed as male. It could also be E-Man or the Midget, or Shitai.
Shitai especially could be a sort of mirror of Madotsuki's own end, but the really obvious answer would be Masada. All of the characters percieved as "Male" could fit into the various types of Animus Evolution Jung presented.
The Athlete:
Midget. The Bike effect, though not a male character, could reflect the animus characteristic of being more like an athelete.
The Planner:
(could be the Demon/E-Man/Flute Guy, since so little is known about them but their context I'm kind of painting a big target around it. Seeing how KyuKyu looks kinda devious even if he's got that constant look of OvO plastered all over his smug face, he could be a more "negative" planner.)
The Professor:
Masada's the most obvious choice for this but he could also be the Guide. Looking at the posters in E-Man's place it almost looks like a consultation or medical office, and manages to make him look a bit more suave/cultured/possibly intelligent than other dream-things.
Guide:
Masada or Shitai, maybe even Cube Guru? Onsen(in the sense of a "Wise Hermit"), Aztec Rave Monkey and E-Man could be looked at as guides too, depending on interpretation. Rave Monkey is quite literally close to being every-god-damn-where in the game, watching over... of course, you could take AzRM backwards and ascribe it to the Shadow.
The Bell Flower/Jellyfish guys could also be guides. They teleport you, seem to appear a lot of places in the dreams, and are also present at Madotsuki's death... they can easily be fit into the Archetype of "Guide"... so can anything that teleports you, really.
The Syzygy:
If one comes to terms with oneself, among other things, the imagery of inseperable pairs integrated to become more powerful/comfortable... the imagery of divine "couples" may show up.
In YN, the usual "pairs" of things are kind of twisted. Monoko/Monoe, Poniko/Uboa, the Train Buddies(little one-eyed things) are all kind of generally messed up. Masada and Madotsuki may be viewed as Syzygy, and so could Madotsuki and Shitai for reasons stated above(death paralell...?) but this one is much harder for me to pinpoint.
Abstractly, using Rain Effect and then Demon/Snow Effect and then Hat+Scarf could represent a Syzygy as two things are used together to produce a more spectacular effect than on their own.
The Child or the Puer:
Er. It says here representation of Innocence. To a point, Poniko's room could represent that, and so could Sky Garden, but that's going into abstracts again. There are several characters that look like Madotsuki(especially igloo girl)... and a lot of creatures in the relatively harmless Neon World could also reflect this idea.
The Self/God Image:
It could be Madotsuki herself but that would be easy, right?
Aztec Rave Monkey watches over everything and may fit this, an omnipresent force in a dream world Madotsuki controls alone. Then again, maybe the Nexus is really the Self? This is the one I REALLY want to hear theories on.