He is childhood friends with Julie Makimoto (before he became her boyfriend later on in the series) and was the top tenth brawler in the world at the start of the season. Like several of the other top-ranked brawlers, he was brainwashed into becoming Naga's servant and opposes the Battle Brawlers until he is freed from Naga's control (although he does win a Brawl). Afterwards, he joins the Battle Brawlers in opposing Naga.
He makes a brief appearance in Bakugan Battle Brawlers: New Vestroia, brawling against Ace Grit along with Julie and traveling the world.
Billy has long hair like Julie, but his hair color is yellow, which is the exact same hair color Marucho has. Billy also wears a t-shirt and a orange and black jacket along with it that has a lightning bolt on the back, wears black fingerless gloves, and a hat that also has a lightning bolt on it.
Billy debuts as a Subterra player together with Julie, where he defeated Julie with his Cycloid. He was later defeated in a rematch by Julie's Gorem.
He becomes the top tenth brawler in the world before he becomes one of Masquerade's henchmen, when he's exposed to the Silent Core. He reappears as Masquerade's henchman, along with Komba O'Charlie, and battles Julie and Shun Kazami. Although he loses, he isn't freed from the mind-control. As Masquerade's henchman, the others often make fun of him since he is the only one in double-digits and is lower-ranked than the rest of them.
Later, when Julie attempts to bring him back to his senses with a battle, he nearly sends Julie and Gorem to the Doom Dimension, but after seeing the toy cowboy and horse he had given her when they were young, he still defeats her but right before Gorem is sent to the Doom Dimension he takes out the Doom Card. He is then freed from Naga's control and, while the Brawlers take Billy back home to Bakugan Valley in Marucho's private jet, he explains to them how he first met Naga.
During Masquerade's quest to strengthen Hydranoid, Cycloid is sent to the Doom Dimension. However, Cycloid (along with the other Top Brawlers' Bakugan) is later freed and reunites with Billy.
He agrees to help everyone stop Naga's minions, and slows Rabeeder's approach on the city though he couldn't completely stop her. He returns to help Julie and Nene fight Tricloid. After they defeat her, Billy realizes he likes Julie, while Julie feels the same way with him, and starts dating. Afterwards, he helps the rest of the brawlers beat Centorrior and Druman eventually winning. He then gets sad to let Cycloid go after Naga is killed.
Billy is first mentioned when Julie says that he was traveling the world to learn from famous athletes, and he was currently living in Spain. He is later mentioned to have moved to Africa to build schools, and finally appears in-person when the Vexos are hunting down the Resistance for the Attribute Energies. He and Julie tag-team against Ace Grit, but are easily defeated. Billy's surprise visit, however, had an unexpected side-effect: it led Mylene Farrow and Shadow Prove right to the brawlers' hide-out.
Bakugan Battle Brawlers
- Subterra Cycloid (Guardian Bakugan)
- Subterra Wormquake
- Subterra Hynoid
- Subterra Tuskor
- Subterra Rattleoid
- Subterra Centipoid
- Subterra Manion
- Subterra Mantris
- Subterra Terrorclaw
- Subterra Saurus
- Billy calls Julie "BakuBabe," which seems to annoy her.
- Also, Billy is similar to Ash Ketchum from Pokémon: The Series. Both characters wore hats that are not the same as the other, however, and that's true because Billy's hat looks a lot like Ash's Indigo League Expo hat, which Ash wore in the first five seasons of the anime, except, in the Bakugan anime, Billy's hat has a orange, white and black color and also has a picture of a lightning bolt on it, just like the description above says.
- In the English dub of the Bakugan anime, Bailey Stocker plays the voice of Billy. Also, in the Brazilian Portuguese dub, both Billy and Ash were voiced by Fábio Lucindo.
- Billy remained as Julie's childhood friend until the end of episode 47, "Here's Mud In Your Eye", where he became her boyfriend after helping her deal with Tricloid.
Bakugan Battle Brawlers
|Bakugan: Battle Brawlers|
|Klaus von Hertzon, Julio Santana, Chan Lee, Komba O'Charlie||No Outcome (interrupted by Masqerade)|
|Shun Kazami and Julie Makimoto (Tag with Komba)||Lose|
|Julie Makimoto||Win (quits Masquerade's team)|
|Rabeeder and Darkus Garganoids (tag with Unknown Bralwers)||Lose (because of Naga)|
|Tricloid (Tag with Julie and Nene)||Win|
|Centorrior and Druman (Tag with Dan, Marucho, Runo, Julie, Klaus, Julio, and Komba)||Win|
Bakugan Battle Brawlers: New Vestroia
|Bakugan: Battle Brawlers: New Vestroia|
|Ace Grit (Tag with Julie)||Lose|