Thread:Mangetsu20/@comment-18812574-20140201220349/@comment-4326112-20140202030522

See, when an Arrancar is born, they are born WITH their Zanpakutou. Re-forming a Zanpakutou would be like trying to rebuild yourself from scratch. If you destroyed your own arm at a spacial level, do you think you can recreate it with limited amount of resources, at an atomic detail? Arrancars may have ONE mad scientist who can possibly do that, and he's dead.

In response to your doubts to my first exclamation, let me say this.

Nnoitra was already enhanced BY the Hogyoku, as Nelliel was (stated in one of their flashback conversations) but after Nnoitra betrayed her and left her for dead, his Zanpakutou changed in shape and he increased dramatically in power. It was a key factor in their battle, that the power from which Nelliel possessed then wasn't enough to beat Nnoitra. So to an extent, Grimmjow and Nnoitra were able to train themselves to a higher level of strength, not necessarily evolve as beings.

As for Yammy, he had been sitting down in the Las Noches cellar for days, eating Hollows, Arrancars and God-knows-what. It was bulking himself up, making him stronger than what he was when he faced Ichigo (Hollows' sole means of getting stronger, at least the weaker ones, was to devour a large amount of spirit-fueled beings). Ulquiorra even meant that he was hard to control, especially in "that state" due to how drunken he was with power.

To answer your response to my theory, hear me out.

The reason why Arrancars don't try and take it off is the fatality rate that exists for just becoming an Arrancar (without the Hogyoku's intervention, that is). Of COURSE there isn't any documentation upon it. Its a fan-based idea. Sometimes even if there's no evidence, you can still base ideas on things you think might be possible. Fanfiction isn't supposed to be entirely spot-on to Canon. Otherwise its just a reiteration of Canon in decent or mediocre text :P

Now as for an alternative...

There was a Fan-based theory that it forms its own identity, which is why (when released) the Arrancar takes a form more like they were as a Menos/Adjuchas/Vasto Lorde. Its basically another being within the blade itself, which is the name of the Zanpakutou (makes you think why their Zanpakutous have names, hm?). Ulquiorra, in this Fan-Webcomic, managed to materialize his Zanpakutou in the same manner that a Captain-class Soul Reaper could materialize their own. This is how he was able to attain the Segunda Etapa, the "Bankai" of Arrancars. Though it was also achieved through a form of Jinzen-like training and having a high amount of Spiritual Power, it is an evolved state that exceeds that of a Ressureccion, which can be treated like a Shikai release since its common for ALL Arrancars.