He was voiced by Christopher Smith.
When Wonderweiss was created, all rationality, speech, long-term memory, and intelligence was removed on purpose to increase his power. This makes him very child-like, much like an autistic person, an example is when he was sent to attack the human world, he just played with a dragonfly. Wonderweiss has shown some signs of hostility, firing a Bala to defend himself at one point, but quickly went back to his child-like state of mind. He does not speak actual sentences and has only ever said a few drawn out syllables, much like an infant. The only time Wonderweiss has spoken clearly was when he told Aizen his name and he is very close to Kaname Tōsen, who regards him as a pure being like himself. He says this is why the modified Arrancar follows him around everywhere and it is implied Wonderweiss is wary of Gin Ichimaru, since he stopped Gin from approaching Tosen at one point.
Creation and Attack on the Human WorldWonderweiss was created by Sosuke Aizen with the Hogyoku and his transformation was attended by many of the Espada. After his change was complete, Aizen asked him if he had a name and Wonderweiss told it to him. The modified Arrancar accompanied Luppi Antenor, Yammy Llargo, and Grimmjow Jaegerjaquez in an attack on the Human World. However all Wonderweiss did was sit around and play with a dragonfly, which made Yammy yell at him for not paying attention to Luppi's battle with the Shinigami. But when Kisuke Urahara showed up, the modified Arrancar attempted to catch him from behind, though Urahara managed to avoid it and launch a counter-attack. Wonderweiss countered with a Bala and Urahara asked him what the technique he'd used was, only to be blasted from behind by Yammy. The modified Arrancar lost interest once again and was soon after brought back to Hueco Mundo, after Ulquiorra Cifer completed his own mission. Later when Grimmjow's arm was healed by Orihime, Wonderweiss and the others watched as he killed Luppi to regain his Espada rank.
Entering the Final BattleAs the battle between the Shinigami and Aizen's forces went on in the fake Karakura Town, Wonderweiss arrived via a gigantic Garaganta. He brought with him an enormous creature known as Hooleer, which Captain Sajin Komamura recognized as the creature seen with the Gillian Hollows that brought Aizen and his cohorts to Hueco Mundo when their plot was revealed. Wonderweiss immediately impaled Captain Jushiro Ukitake with his hand, letting him fall to the ground and Captain Shunsui Kyoraku attempted to attack him. However Coyote Starrk, who'd been fighting the two earlier, blasted him with a Cero to send him falling as well. Starrk remarked that Wonderweiss' arrival meant that Aizen had grown tired of the battle and the modified Arrancar used his battlecry to shatter the ice obelisk that was imprisoning Tier Harribel, as well as clear away the smoke around Baraggan Louisenbairn generated by Captain Suí-Feng's attack to show it had no effect. As Wonderweiss continued to let loose his cry, Hooleer expelled a host of Gillians from its mouth. However the Visored, Mashiro Kuna, attacked and destroyed Hooleer with the modified Arrancar looking on, shocked at the loss of his companion. Wonderweiss proceeded to charge his Cero, but Mashiro kicked him in the face, stopping the attack. But the modified Arrancar didn't go down so easily and lunged at Mashiro twice, only to be smashed away both times. Wonderweiss managed to grab the Visored by the scarf and threw her away through several buildings before they launched themselves at each other. Mashiro fired her Mashiro Super Cero at the modified Arrancar, but he countered successfully with his battlecry. The Visored launched punches at Wonderweiss, when her Hollow mask shattered and taking the advantage, he delivered a strong blow to her face, knocking her out. However when the modified Arrancar attempted to strike her again, Kensei Mugurama, another Visored, caught his fist and threw him into several buildings. Kensei put Mashiro in a safe area and talked to her for being reckless, then Wonderweiss emerged to attack the Visored. Kensei released his Bankai and the two attacked each other, generating an enormous explosion.
Fighting with YamamotoLater while Head Captain Yamamoto was fighting Aizen, Wonderweiss appeared behind him in Resurreción form. Yamamoto, having sensed his presence, moved to attack the modified Arrancar, but was shocked when Wonderweiss caught the blade and threw him away. The Head Captain wondered how the modified Arrancar could negate the flames of his Zanpakuto, Ryujin Jakka, and Aizen explained that he knew he couldn't match Yamamoto in one on one combat. He then explained that Wonderweiss had been the only modified Arrancar he'd created and that he'd been specifically created to negate the powers of Ryujin Jakka. With his Zanpakuto gone, Yamamoto changed to hand-to-hand combat and succeeded in landing a blow that punched a hole in Wonderweiss' torso and sent him flying into a building. The Head Captain attempted to attack Aizen again, only for the modified Arrancar to stop him and multiple arms emerged from his shoulders that he used to attack Yamamoto, while his torso regenerated. However the Head Captain was unfazed by this and tore off Wonderweiss' arms, then stated he was glad that the modified Arrancar wasn't in his child-like form any more. Yamamoto then used the powerful technique, Sokotsu, utterly destroying Wonderweiss and shattering his body. His remains fell to the ground below, exploding and releasing the fires he absorbed from Ryujin Jakka before.
PowersWonderweiss possesses great spiritual power that is stated to be at the same level as the Espada and mainly utilizes hand-to-hand combat. He does not seem to use any particular combat style, using punches and grabs, and throws himself into battle with no regard to any damage he may take. Wonderweiss can use a Cero, a powerful energy blast used by Arrancar and Hollows and his is a purple one that he charges from his mouth. He can also use Garganta, a portal that allows Aizen's forces to move to and from Hueco Mundo, Bala, a concentrated blast of the user's spirit energy fired from their fist that is 20 times faster than a Cero, Hierro, a technique that makes the user's skin almost impenetrable, and Sonído, an Arrancar technique that lets them move at super speed. Wonderweiss possesses superhuman strength and can unleash a "battlecry", a powerful banshee-like sonic cry that also seems to be a way of controlling Hooleer. Like all Arrancar, he can enter his Resurreción form by releasing his Zanpakuto, Extinguir, though the release command is unknown. In this form, Wonderweiss gains an increase in power and can seal the power of Yamamoto's Zanpakuto, Ryujin Jakka, trapping any new fire within the blade and all the current fire in his own body. He is also granted an enhanced Hierro, greater strength, high-speed regeneration, and the ability to let loose numerous arms from his shoulders that can stretch to grant lengths.
- There is a minor animation error with Wonderweiss. When he impales Ukitake with his hand, it is his left hand, but the hand he removes is his right one, covered in blood.
- The name of Wonderweiss' Zanpakuto, Extinguir, is "To Extinguish" in Spanish and "Prince of Extinguished Flames" in Japanese, a reference to his Resurrección form's ability to negate the fire powers of Yamamoto's Zanpakuto.