Teddy Altman

Teddy is a former member of the currently disbanded Young Avengers.

Young Avengers Disbanding
After taking down Kang and battling away the Skrull and Kree armies when they tried to abduct him as their savior, the Young Avengers, for the most part, disbanded. With so many larger heroes and less villains around, there was no need for the team anymore. And, for a short period of time, Teddy left the city.

When he returned, he found his boyfriend, Billy Kaplan, had accidentally hurt someone and joined the Xavier's Institute to better control his powers. Thinking that Billy had moved on and couldn't forgive him for running off on his own, Teddy broke up temporarily with his boyfriend. After getting an earful from Billy's spirit-brother, Tommy Shepherd, and realizing his mistake, Teddy apologized and the two reunited.

Gaining a Third and Getting into Shenanigans
As a thank you to Tommy for bringing the two back together, Teddy and Billy decided to take him out to eat. After that, the next few days were filled with harmless teasing and fun until it turned into outright flirting. The final push was one night where Tommy snapped a topless picture of Billy and teased Teddy that he wanted a matching set. By the end of the night, the three had slept together but were still fairly uncertain about their relationship, especially with the complications of Tommy 'technically not but technically being' Billy's brother. But the three gave it a shot regardless.

For awhile, Teddy did to a degree feel left out. Billy and Tommy were spending much more time together since Tommy slept at the mansion while Teddy secretly lived in an apartment on his own. But that all changed when Tommy and Teddy decided to go out on a date themselves. At first, it was a bit awkward. Tommy learned that Teddy could transform himself into animals and Teddy learned his stomach didn't like the speeds Tommy ran at. But by the end of the date, the two got ended up buying a "sexy Captain America" outfit for Billy and went to his dorm to give it to him.

After a few laughs and some fun, Teddy off-handedly said he should put on the outfit and shapeshift. Claiming Teddy couldn't take it back, Tommy convinced him to actually do it. By sheer happenstance and very much misfortune, after Teddy came out transformed as Steve Rogers in the garment, Agent Phil Coulson walked into the room. Mortified, Teddy turned into a pug and hid in the bathroom until the agent left.

Dreams & Nightmares
When the Scarlet Witch went insane and reshaped the world into a utopia, Teddy's paradise consisted of himself as Savior of the Kree and Skrull worlds. He had accomplished many things by them, including stopping the long war that raged between the two and bringing them peace on the neutral lands of Earth. His foster mother, who had died in the real world during his run-in with the Super Skrull, was serving as his personal maid while his bodyguard was Noh-Varr. But even after all his accomplishments, he still felt as though something in his life was missing.

Billy and Tommy found Teddy first. Since Wanda did not know of their existence and the two were anomalies in the universe to begin with, they were free from her spell. Billy used his magic to make Teddy remember his past life, which triggered the boy to have a breakdown. After calming down, he agreed to help the two fix the mess and bring Wanda to her senses.

By the time the trio got to Wanda, the Scarlet Witch had already become fully possessed by Mephisto. He used her body and powers to fight back. Protecting Billy from one of her spells, Teddy ended up disintegrating before his body could heal and regenerate himself, dying.

After Billy and Tommy managed to break Wanda from her spell, the twins and the witch combined their energies to garner enough to revive Teddy. He woke up just in time to see Billy slip into a comatose state.

After Stephen Strange aided Wanda in mending the world, Billy woke up to find a ring slipped over his finger. Having already given Teddy his blessing while Billy was asleep, Tommy excused himself from the room shortly after as Teddy proposed to him on the spot. Billy accepted.

The Creation of Theo
After his engagement, everything got a little rougher. Tommy vanished and Billy thought it was because of the engagement. So, taking Teddy aside, Billy explained that perhaps it wasn't the best time for them to get married. Teddy put on the best act, making it seem like he was completely okay with it, but he wasn't. He couldn't handle the rejection and his insecurities got the better of him.

Flying up to a skycraper, Teddy has a full blown panic attack. After a moment of depression, he regretfully wishes that Tommy had never joined in his and Billy's relationship and, immediately after, he felt massive amounts of guilt. He decided then that he didn't want to be Theodore Altman anymore. So, he created a new persona to be - Theo.

But Theo brought Hulkling nothing but bad influences.

Powers
Being half Skrull and half Kree, Teddy possess the powering of super strength and shapeshifting. He has used this to transform into different people, taking on the identities of various heroes. He has also shown that he can use those shapeshifting abilities to turn into animals, particularly a dog.

Alternative Universe Plots

 * Theodore Altman in the Pirates AU was a ex-cabin boy. His ship was taken over by Davy Jones, who cursed the crew to become part of him, but Theodore managed to jump ship before the curse took full effect. Because of this, during the day he turns into a barnicle-covered green monsters, but during the night keeps his human form.