Bawabawa

Bawabawa is a giant worm-like Hollow that lives inside Dondochakka Birstanne's stomach and comes out when the group needs to cross Hueco Mundo. He is their transport, their pet, and a willing participant in the endless game of tag that Nelliel Tu Odelschwanck and her two Fracción play across the sand.

That game is how Ichigo Kurosaki's group meets all of them, and they read it completely wrong. Watching an enormous Hollow chase a small child, Yasutora Sado attacks it, and Nel has to stop him and explain that Bawabawa is losing on purpose. It is the first sign that Hueco Mundo is not the uniform horror the Shinigami describe.

He does not speak and he does not fight in any serious way. What Bawabawa is for is the same thing Pesche and Dondochakka are for: keeping a former Espada who has been reduced to a child entertained and moving and unaware of what was done to her. A giant worm playing tag in the desert is an absurd image, and it is doing exactly the work the arc needs it to.