“Growing up, I didn’t see anyone like me on TV,” says RJ Mitte. On first glance, this seems unlikely. With his camera-ready smile, sharp suit and dark swoop of glossy hair, Mitte appears so made-for-television it is as if he has been cooked up in a lab by his former on-screen father, Breaking Bad’s Walter White. But Roy Frank Mitte III (RJ stands for Roy Jr) isn’t talking about his looks.

The 22-year-old has cerebral palsy, a neurological condition he shares with the character he played in what has been dubbed the “best TV show of all time”, though in a less severe form than his character’s. Cerebral palsy affects movement and coordination, but Mitte walks unaided, and his speech is much clearer than the slurred voice he adopted to play Walt Jr. As a young boy, he spent years with his legs in braces to stretch the muscles, while physio and speech therapy were part of his daily routine.

“The closest person on screen was Forrest Gump – that was my representation,” he says. Then he laughs at the black humour the film sparked in his family. “I played soccer for six seasons in braces and casts, and my mother would yell: ‘Run, Forrest, Run!’”

When Mitte read the character summary for Walt Jr seven years ago, it came as a welcome shock. “The breakdown pretty much described me,” he says, still slightly amazed by his luck. “Dark hair, big eyebrows, cerebral palsy … I was like, ‘I have this covered.’”

Mitte as Walt Jr in Breaking Bad, with Bryan Cranston as Walter White. Photograph: Ursula Coyote

The similarities between Mitte and his character were not merely cosmetic. In Breaking Bad’s first season, for instance, Walt Jr is preyed on by vicious bullies, something Mitte himself had experienced. “I was pushed, shoved, had my hand broken, had my foot broken. They kicked my hand, stomped on it. The same with my foot,” he recounts, matter-of-factly. “When you have a disability, people think you are weak. They think they can prey on you.”

How did he deal with it? “I stood my ground. I grew up with a marine grandfather. I was never allowed to say ‘can’t’ or ‘no’, and I was never allowed to back down.”

So he fought back? “Pretty much. They would try to fight and I would defend myself.”

It is obvious the experience affected him deeply. For the majority of our interview, Mitte exudes all-American warmth, but when he talks about bullies and prejudices, his condemnation is almost biblical. “They are dwelling on hatred and think they can take advantage of people they think of as weak,” he says. “But people like that don’t thrive or grow. They will never evolve as a person and deal with true, genuine kindness.”

Mitte as Walt Jr. Photograph: Ben Leuner / AMC/Ben Leuner/AMC

Mitte is a passionate campaigner for disability charities, including I AM PWD, which aims to increase the number of performers with disabilities. He tours schools, giving talks about his experiences, encouraging disabled students to build up the mental resistance that he believes is essential to their self-esteem.

“People with disabilities can grow up thinking they have a weakness because they are told: ‘You will never do this properly, you will never walk properly or talk properly.’ That’s all they hear. But you have to look past that.”

When Mitte was first given the chance to act professionally, at 13, his mother almost put a stop to it. His one-year-old sister had secured a part in a commercial, and his mother decided the family should move from Texas to Los Angeles. When she approached agents to represent the toddler, one suggested they could find work for Roy Jr, too. His mother was less than enthusiastic. “She said: ‘You know, this business can be very negative and we don’t want that aspect of it. He has CP and … we don’t want that negativity [in his life].’”

Mitte says he understands her reluctance. “This business is very big on how people look,” he says. But the teenager had other ideas. He had been home schooled, while his single mother cared for her dying parents, and now he wanted something to do, and a way to make new friends.

“If you move to Los Angeles and you don’t go to school, you don’t join a gang and you don’t act – well, you aren’t doing anything else,” he says. “That’s about it.”

Mitte as Campbell in the ABC series Switched at Birth. Photograph: Eric McCandless/ABC

Five auditions later and Mitte was on set in New Mexico, for the show he would star in until he was 20. Since Breaking Bad ended in 2013, Mitte has played a returning character in the ABC teen drama Switched at Birth and the lead in the yet-to-be-released indie film Who’s Driving Doug, and he has just finished filming another movie, Dixieland, alongside Lisa Marie Presley’s daughter Riley Keough. They may not be the most eye-catching roles but, chatting to him about his schedule of meetings and appearances, it is obvious he is working hard to increase his profile.

When I ask him if he thinks he will struggle to land major roles as an actor with a disability, he insists he does not think about it. Nor is he worried about being typecast: “You accept the risks and you accept these will be the parts you play. But it’s all about how you play those parts – you have to show the inner strength that people have.”

He thinks there has been a genuine shift in the perception of disability on TV since he began his role on Breaking Bad, citing the number of disabled regular characters on prime-time scripted series. “In the States, when I started, there were five and now there are 11.” But, he says, disability is still too often seen as a liability when it should be seen as an asset, both in actors and the characters they play. “Without [my] disability I wouldn’t understand half the things I do today. You grow, you learn and you suffer – and it gives you more understanding of aspects of this world.”

One internet meme has Walt Jr pictured with breakfast over and over again, the suggestion being he was more plot device than rounded character for the first few seasons. Did he get fed up with playing the part? He sounds shocked. “No! Never. I could have played him for a lot longer.” He would, though, have liked for his character to have had a few more twists. “You got to see a little bit of Junior but not all of him,” he says. “I would have liked him to stretch his wings.”

So would he be happy to be known forever as Walt Jr? “Nothing I do will ever compare with Breaking Bad,” he says with diplomatic charm – and then, with that trademark confidence: “I have better performances in me.”