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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, their mother sung them a Sokovian Lullaby to get them to settle. When she recognised the name 'Pietro', Geraldine (really Monica Rambeau) enquired about Wanda's history with Ultron and disrupted her fantasy. Becoming more and more aggravated, Wanda interrogated Geraldine about how she knows Pietro. In response to the adults' confrontation, Billy and Tommy started to cry until Wanda used her powers to eject Geraldine from Westview. Billy and his brother calmed down again once Wanda returned to them.
Growing Up Fast
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- "Halloween's a magical holiday. All about family, friends, and the thrill of getting to be someone else for a day."
- ―Billy Maximoff[src]
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Abducted by Agatha Harkness
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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.
- 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.
- 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.