|Affiliation||Aizen's Arrancar Army|
|Occupation||Arrancar #77 in Aizen's Arrancar Army|
|Base of Operations||Las Noches, Hueco Mundo|
Wonderweiss has a thin and somewhat childlike body. He has light blond hair, parted to one side, with the tips fanning out from his face. The remains of his Hollow mask consist of a three-point tiara on the top of his head. He only has two teeth visible when smiling, freckles and bright purple eyes. He wears the Arrancar jacket with a hole in the middle of his chest, revealing his Hollow hole and the tip of a mark on his chest. The outfit also has large arm cuffs on the sleeves.
As a Hollow, he was roughly humanoid in both size and shape. Even though his body was wrapped in bandages during his birth, several protrusions could be seen throughout his body.
According to Aizen, all forms of rationality, memory retention, speech, and intelligence were purposely removed to enhance his power. Because of this, Wonderweiss' personality is very childlike, comparable to someone with low functioning autism. For example, when sent on a mission to kill, he instead played around with a dragonfly. He shows some hostility, firing a defensive blasts at one point, but quickly reverts to his usual childlike state after doing so.
Wonderweiss does not speak in sentences due to his modifications, only saying a few drawling syllables at a time such as an infant would. The only coherent phrase he has ever spoken is his own name, immediately after being "reborn" as an Arrancar. Kaname Tōsen remarks that Wonderweiss, like himself, is a pure being (though he remarks he doesn't quite know what exactly is pure about him) who often tend to stick together. He claims this is why Wonderweiss follows him everywhere. It is implied that he tried to restrain Gin Ichimaru from approaching Tōsen because Wonderweiss was wary of him.