Board Thread:Questions and Answers/@comment-13442349-20130726072748/@comment-24074672-20131103190254

N-e-ls wrote: Once you become a Hollow, you can never become anymore a Plus. That's what Rukia tells Ichigo in chapter 6. A Hollow that looks similar to a human is simply an Arrancar. By removing a part of their mask, they gain a part of their sanity. Anyway, I wonder about Starrk and Harribel. They've never shown any Hollow traits in their personality, that is, they're fully sane.

No, you're wrong, a Hollow that look similar to a human is a Vasto Lorde.

Arrancar are Hollows granted Shinigami powers via the Hogyoku. This means arrancar are not part of the Hollow Evolution.

Hollow --> Gillian (Aaronierro) --> Adjuchas (Grimmjow) --> Vasto Lorde (Harribel).

Whether you're a normal hollow or a vasto lorde, you can become an arrancar.

In Starrk's & Harribel's case, they were already a Vasto Lorde before they met Aizen...Hence why they are Espada 1 & 2, respectively.

Grimmjow was an Adjuchas and Aaronierro was a Gillian