Eventually, Agatha Harkness puts Billy and Tommy in captivity to force Wanda to reveal how she caused Westview Anomaly. During the Battle of Westview, they are freed by Wanda and help her defeat the S.W.O.R.D. as she battles Agatha Harkness. In the end, Wanda undoes the Westview Anomaly, causing Billy and Tommy to disappear along with it, but then she hears the twins scream for her help as she studies the Darkhold.
After an unnaturally fast pregnancy, Billy Maximoff was born shortly after his twin brother Tommy to their parents, Wanda Maximoff and Vision, in their Westview family home. After being checked over by Dr. Stan Nielson, the new-born twins were put to bed as Wanda and Geraldine watched over them. After reminiscing about her own twin brother, Wanda sung them a Sokovian Lullaby to get them to settle. When Geraldine recognized the name "Pietro", she enquired about Wanda's history with Ultron. Becoming more and more aggravated, Wanda interrogated Geraldine about how she knew Pietro. In response to the adults' confrontation, Maximoff and Tommy started to cry until Wanda used her powers to eject Geraldine from Westview. Maximoff and Tommy calmed down again once Wanda returned to them in their crib.
Growing Up Fast
Shortly after Maximoff and Tommy were born, Wanda Maximoff and Vision grew increasingly frustrated as the twins refused to sleep and instead were crying. As Wanda and Vision were attempting to get their newborn children to sleep, Agnes walked into the house. She offered to take care of the babies for them to relieve some of their stress. Eventually, the exhausted parents noticed that the children were quiet, but soon realized they were not in their cribs. They soon realized that the twins’ ages had accelerated and that they had magically grown from newborns to five-year-olds.
Later, Maximoff and his brother found a stray dog in their street, and brought him to their kitchen, intending to bathe him so their mother would let them keep him. When Wanda discovered the dog, she warned them that taking care of a dog was a huge responsibility. Vision later walked in as well, and so did Agnes, carrying a doghouse for the new family pet, whom they named Sparky. However, when Vision insisted that the twins were not old enough for a dog, Maximoff and Tommy looked at each other mischievously. They then aged themselves once more, this time to ten-year-olds.
Later that day, Maximoff trained Sparky to do tricks and fed him treats. When Tommy insisted that they go to show their father, Wanda informed them that he was at work. The twins found this confusing as it was a Saturday, so he wasn’t supposed to be working. Wanda told them he needed a distraction. However, Maximoff believed that he needed a distraction from them. Wanda quickly explained that that wasn’t the case, and said to them that while he and Tommy would argue at time, they would always be brothers. Tommy asked if Wanda had a brother, and Wanda said that she did, but that he was far away from here. The twins and their mother would then be distracted by Sparky running to the door, something attracting his attention. As Wanda went outside to investigate, she opened the door only for Sparky to run away, which caught Maximoff and Tommy’s attention. Maximoff and Tommy then went outside to find a headed towards their mother.
Shortly after, Wanda, Maximoff and Tommy were walking around their street looking for Sparky, who had run away earlier. They soon were approached by Agnes, who was holding Sparky in a blanket, and she informed Maximoff and Tommy that he had died. The twins were shocked and devastated, and attempted to again age themselves, however Wanda stopped them before they could do anything. They begged for Wanda to resurrect Sparky, however Wanda insisted she couldn’t do such a thing. Vision arrived soon after and saw that Sparky had died, and comforted his sons.
- "Halloween's a magical holiday. All about family, friends, and the thrill of getting to be someone else for a day."
- ―Billy Maximoff[src]
The next day, Maximoff got dressed into his Halloween costume and talked about Halloween while getting video-taped. He then joined Tommy in pranking "Pietro Maximoff", who was lying on the couch. Shortly, Wanda Maximoff walked down the stairs, in her costume, and then greeted Vision who joined them in his costume. Maximoff then watched as "Pietro" whisked Tommy away and then returned wearing matching costumes and hairstyles.
Maximoff then enjoyed the Halloween festivities with Tommy and "Pietro". Later that evening, Maximoff and Tommy approached Wanda and showed her their newfound powers. Maximoff was able to telepathically move objects, like his mother. Maximoff and Tommy then left to get candy at the end of the street, before returning to the main square. Maximoff then used his powers to halt an excited Tommy, as he used his mind to see Vision in distress outside next to S.W.O.R.D. agents, and immediately rushed to inform Wanda. Maximoff then watched in shock when Wanda used her powers to blast "Pietro" into a haystack.
The next morning, Maximoff and Tommy played video games in the living room, while waiting for their mother to wake up. However, their games began switching throughout different time periods. Confused, Maximoff and Tommy went up to Wanda's bedroom and asked her what was happening. However, Wanda didn't want to be bothered and told them she wanted to sleep. Maximoff then told her that he could hear voices in his head, meaning that he could hear the other Westview citizens.
Maximoff and Tommy then returned downstairs and waited for Wanda. When she came down, she told them to stay away from "Pietro" and that Vision would return when he was ready. She then began to have a mental breakdown, confusing Maximoff and Tommy.
After Wanda sat down with them, Agnes arrived and walked inside. Seeing that Wanda was stressed out, she then offered to watch Maximoff and Tommy at her house while Wanda got feeling better. Wanda agreed and Maximoff and Tommy left with Agnes.
After being taken to Agnes' house, Maximoff and Tommy sat down on the couch in the living room and Maximoff played with Señor Scratchy, who laid in his lap. When Agnes joined them on the couch, Maximoff told her that she was silent and that he couldn't hear her thoughts. Agnes then reassured them that their mother would be fine. Agnes then made Maximoff and Tommy sandwiches and turned on the television for them, before locking them up in her witch lair.
Maximoff and Tommy were then brought out to the street by Agatha Harkness and restrained by her magic, causing them to choke. They then cried out when they saw Wanda run out and try to rescue them. After Harkness declared Wanda the "Scarlet Witch", Wanda blasted Harkness away, allowing Maximoff and Tommy to run into their house.
Inside the house, Maximoff saw a vision of Wanda in the Westview town square and told Tommy that she needed help. After running to the town square, however, Maximoff and Tommy fell to the ground and began to disappear as Wanda was getting rid of the Hex. When Wanda saw this, she stopped and embraced Maximoff, Tommy, and Vision. Wanda then put a force field around them as Agatha Harkness tried to shoot them with her powers. After Harkness had absorbed Wanda's powers, S.W.O.R.D. agents in Humvees arrived, followed by White Vision. Wanda told Maximoff and Tommy to handle the agents while she dealt with Harkness.
Maximoff then used his powers to mind control the agents, while Tommy sped around and took some of the agents' belongings. Maximoff then watched as Tyler Hayward stepped out of his Humvee and aimed at them with his gun. However, they were saved by Monica Rambeau.
Rambeau used her new powers to absorb the bullets, but when she missed one, Maximoff stopped the bullet and threw it to the ground. Hayward, enraged, hopped into another Humvee and prepared to ram them, but was ultimately prevented from doing so. Maximoff then told Rambeau that he liked her powers. They then ran over to meet with Vision, and then watched as Wanda fought Harkness in the sky.
Maximoff then reunited with Wanda, having embraced her role as the Scarlet Witch, and watched as she transformed Harkness back into "Agnes". Maximoff then left the town square with his family and returned home. There, Wanda and Vision tucked Maximoff and Tommy into their beds and said there goodbyes, while the Hex was getting torn down.
Maximoff smiled for the last time after Wanda thanked him and Tommy for being their mother, before he and Tommy disappeared.
Billy's Voice Heard
Billy Maximoff is considered the more "dorky" twin, according to Tommy Maximoff. Maximoff seems to be interested in Halloween, calling it a "magical holiday" and mentioning that it is full of family, friends, and dressing up as someone else. He is also the only twin to have a costume prepared ahead of time. Conversations with his brother hint that he is intelligent. Maximoff is also shown to be concerned about his mother when she seemed to be especially depressed.
- Psionics: Like his mother, Billy Maximoff has psionic abilities, which manifest as blue, glowing energy currents and mist-like shapes from his hands.
- Psionic Energy Manipulation: Maximoff has the ability to create and manipulate psionic energy.
- Telepathy: Maximoff was able to telepathically hear and feel Vision in distress while escaping from Westview.
- Precognition: Maximoff was able to see his mother smothering Westview civilians before it happened.
- Age Manipulation: Maximoff and his twin brother Tommy have both been shown to have the ability to change their ages at will, each time aging up around 5 years.
- In the comics, Billy and his twin Tommy were magical constructs created subconsciously by Wanda Maximoff using pieces of Mephisto's soul. Billy eventually ceased to exist, only to be reincarnated years later in Billy Kaplan, also known as Wiccan, for his magical, reality-warping powers like his mother. He is also a member of the Young Avengers.
- Billy was named by his father Vision, who named him after William Shakespeare.
- Billy usually wears red while his brother wears green, a reference to their comics reincarnations' costumes.
- During his first Halloween, Billy's costume closely resembles the super-hero uniform of Wiccan.
Behind the Scenes
- Jack Fisher auditioned for the role of Billy Maximoff.
- Jackson Robert Scott was a reference for Billy Maximoff in On a Very Special Episode... and All-New Halloween Spooktacular!.
- Brittania Fader was a stunt double for Julian Hilliard in the role of Billy Maximoff.
- WandaVision: 1.03: Now in Color
- WandaVision 1.05: On a Very Special Episode...
- WandaVision 1.06: All-New Halloween Spooktacular!
- WandaVision: 1.04: We Interrupt This Program
- WandaVision 1.07: All-New Halloween Spooktacular!
- WandaVision 1.08: Previously On
- WandaVision 1.09: The Series Finale
- WandaVision 1.09: The Series Finale Post-credits Scene
- Jack Fisher - Audition Tape for WandaVision