Billy and Teddy were both selected for the Avengers Fail-Safe Program (a program designed to assemble a new team of superheroes in case the Avengers were disbanded), and joined the Young Avengers with team members Iron Lad and Patriot as Asgardian and Hulkling. The two began dating not long after.
The couple seems to have grown close over a significantly short time, as Teddy states during the attack of Kang the Conqueror that Billy learned his spell-casting from reading Teddy's mother's self-help book.
After having prevented the destruction of the timeline, Billy having officially changed his code name to Wiccan, he decided now would be a good time to reveal his aspiring superhero identity to his parents. However, the Kaplans misread his intentions and assumed he was coming out about his relationship with Teddy. Nonetheless, they were very supportive of the two, and even went so far as to call Teddy an "excellent son-in-law".
When Teddy is shot during the attack of a terrorist group, he is taken hostage and the gunman threatens to detonate a nuke strapped to his back. Sensing that his boyfriend was in grave danger, Wiccan's powers overloaded and sent the entire group comatose.
Whilst attempting to stay on Billy's side, Teddy is afraid of what would happen if Billy lost control of his powers again. Agitated, Billy dismisses Teddy's attempts at a conversation and leaves, only to run into Captain America in his home. The man convinces Billy to come with him to the Avengers Tower for a testing of his powers, but they are soon stopped by Hulkling. Teddy warns Captain America that if anything happens to Billy, he should not be worried about the boy but rather what Teddy would do, and that where Billy goes, Teddy follows. Surprisingly to the couple, Captain America is not troubled by this and in fact invites Teddy to share a room with his boyfriend during the course.
The room turns out to be something more akin to a dungeon, but Wiccan uses his magic to transform the twin beds into a king-sized one. The pair begins to embrace, and Billy apologizes for the events that transpired, and Teddy assures him that what happened was out of his control and the Avengers's tests would be harmless. The couples tries to kiss, but is soon interrupted by an unhappy Tommy, whom transports the involuntary couple out of the tower. The touching reuniting moment is stalled by the appearance of Magneto, the twin's grandfather.
When the Avengers attack Magneto, Teddy is seen protecting Billy from danger on numerous occasions, as when Wolverine tries to kill him. Teddy also humorously expresses that he's never been as attracted to Billy when he decides to not give a damn what the Avengers will do to him and brings the entire team and Magneto to Transia. Teddy objects to Billy's idea to send them home, and he is convinced by the team to let them help. To make their attire less suspicious-looking, Billy transforms their clothes into those of the movie "Sound of Music", Teddy explaining that it is Billy's favorite film, to which his boyfriend interjects saying that it is one of his favorites.
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