Warning! This article contains spoilers for Episode 6 of Agatha All Along

Summary

Joe Locke's Teen character has been identified as the son of Scarlet Witch.
William Kaplan becomes Billy Maximoff after his soul is transferred from Wanda's Hex.
A magical sigil placed on William by Lilia prevents him from revealing his identity.

Agatha All Along finally provided more information on Joe Locke's mysterious Teen in Episode 6, answering long-held questions and confirming a few fan theories. Locke's character's identity had been a mystery up until the end of Episode 5 of the Disney+ series, thanks to a magical sigil that stopped the witches from learning his true name.

Agatha All Along continues the story of Agatha Harkness who was introduced to fans as the antagonist in Marvel's WandaVision. In Agatha All Along, the infamous witch gathers a coven to help her pass the trials of the Witches' Road, which grants the survivors whatever they most desire. So far in the series, each trial on the road has been more deadly than the last, and with the fearsome Salem Seven in pursuit of Agatha, it's meant not every witch who joined the coven has made it out alive. Just like WandaVision, Agatha All Along has featured plenty of twists and turns, and the one regarding Teen's identity has finally unfolded.

Who is William Kaplan?

Joe Locke as William Kaplan in Agatha All Along

Cast	Kathryn Hahn, Aubrey Plaza, Joe Locke, Patti LuPone, Sasheer Zamata, Debra Jo Rupp, Ali Ahn
Showrunner	Jac Schaeffer
Number of Episodes	9
Streaming on	Disney+

In Episode 6 of Agatha All Along titled "Familiar by Thy Side," audiences are given a resolution to the previous episode's cliffhanger, which revealed that Joe Locke's character, Teen, was the son of Wanda Maximoff, aka the Scarlet Witch. The last Wanda's children were seen was in the final episode of WandaVision, when they vanished along with the hex that had been controlling the residents of Westview.

The events of the WandaVision finale also impacted a 13-year-old Jewish boy named William Kaplan, who was driving home with his parents, Rebecca and Jeff, on the night of Wanda and Agatha's climactic battle. After watching the giant red dome of the hex malfunction through the window of their car, the Kaplans get into a car accident which leaves William unconscious. When he awakens afterward with a head injury, William is confused and has limited memories of his life before the accident. He finds he suddenly has the ability to hear the thoughts of those around him.

How William Kaplan Learns His Identity

Three years later, William has become hellbent on learning about his past, which has resulted in an obsession with witchcraft and its history. He and his boyfriend Eddie arrange to meet a stranger who promises to reveal to them what happened inside Wanda's Hex. This stranger ends up being Ralph Bohner (Evan Peters), the man Wanda co-opted as her brother, Pietro, in her fantasy life. Ralph reveals to them that Wanda had constructed twins, Billy and Tommy, inside the hex, which leads William to realize that this is who he has become.

How Did Billy Maximoff Become William Kaplan?

The process of how Billy Maximoff became William Kaplan isn't thoroughly explained but is similar to what happens to the character in Marvel Comics. Essentially, the magic that Wanda tapped into to create her fantasy life in Westview was strong enough to make her twins, Billy and Tommy real. This meant that when Wanda ended her spell, the souls of the twins were released with nowhere to go. When William Kaplan died in the car crash near Westview, it seems Billy Maximoff's soul was attached to the nearest available vessel, which allowed him to be reborn in William's body.

Who Created Teen's Sigil in Agatha All Along?

After speaking to Ralph Bohner, William Kaplan knew he was truly Billy Maximoff, but he wasn't able to tell any of the witches (or the audience) this due to a magical sigil that was placed on him. The caster of this sigil was revealed in Agatha All Along Episode 6. During William's bar mitzvah on the night of the accident, he received a palm reading from the witch, Lilia Calderu (Patti LuPone). Lilia was surprised to find that William's lifeline was split in two, clearly foreshadowing his death and rebirth later in the night. It seems that Lilia may also have been able to foresee who William was going to become in his next life, and cast a sigil on him to help keep his identity obscured from other magic users, including herself.

Why Did Lilia Cast the Sigil?

Given that Billy Maximoff is the son of the ultra-powerful Scarlet Witch, and inherited some of her power, it seems Lilia might have cast the sigil to keep him safe from any who might seek to take advantage of that. It took William over three years to learn his true identity as Billy, and in that time he would have been vulnerable to all sorts of enemies. After unlocking his power in Agatha All Along Episode 5, Billy breaks the stone carrying Lilia's sigil, which allows him to finally speak his true name and reveal his identity to Agatha. While Billy still has a ways to go before he becomes his superhero alter-ego, Wiccan, his trials on the Witches' Road are quickly transforming him into the young Avenger from Marvel's comics.