The 48-year-old’s family have given a rare insight into the actor’s early life, revealing how he overcame nasty taunts at school, dodgy haircuts and even getting trapped in a treasure chest to play Tyrion Lannister in the hit TV show.
In a world exclusive sit-down chat with The Sun Online at his childhood home in Morristown, New Jersey, family and friends told how he was treated like a “novelty” at school after being diagnosed with achondroplasia – a common form of dwarfism.
Standing at just 4ft 5in, he is the only dwarf in his family, but mum Diane said he was always determined his disability would not affect him.
But despite his positive attitude he had a hellish time with doctors as a child and was actually stretched in a bizarre attempt to cure his condition.
The former music teacher said: “When I gave birth to him I knew something was wrong, but I didn’t know what. The doctor was unsure if Peter was a dwarf.
“It would have been better if he’d said he was, because I was always wondering about it.
“They used to stretch out his little arms and legs like a Stretch Armstrong doll.”
Before he was old enough to walk, Peter was diagnosed with the genetic disorder where the arms and legs are shorter, but the torso is of average length.
Diane, 74, said: “There was no internet then, so we didn’t know much about the condition.
“I only knew dwarves to be in circuses and The Wizard of Oz movie.
“We went to the top geneticists in the country, and he had an operation on his legs, they were bowed and had to be straightened out.”
She told how they had to be creative at the family home to suit Peter’s needs – such as letting him climb up on to the kitchen counter to reach boxes of cereal with a pair of kitchen tongs.
Despite his diminutive stature Peter thrived at school and “never complained about kids teasing him”.
Diane Lopez, his former drama teacher at Delbarton – an all-male Roman Catholic school in Morristown – praised the way he dealt with people making fun of his height.
She said: “Peter always had extreme presence, right from the get-go.
“He was confident and hung around with a tight-knit group, but I don’t think it was easy for him.
“I think maybe some children saw him as a novelty, and I remember one of the teachers saying he should ‘get to know and hang out with other little people.’
“I’m glad he didn’t listen to that … he wanted to be recognised for his own worth.
“Kids say stupid things, they don’t mean to, but it can really hit the core. I don’t think he showed it bothered him, he covered it well. I never saw him upset.”
Incredible photos from Peter’s official yearbooks in 1986 and 1987 show him horsing about with pals, performing a version of the Miami Vice theme song and showcasing a rather lustrous mullet haircut.
Peter went from strength to strength with his acting, playing the lead in his school production of The Velveteen Rabbit and going on to study drama at Bennington College.
He later moved to New York, living off friends’ sofas because he had so little money, before managing to launch his own theatre company with a friend.
He refused to play “demeaning roles” like elves and leprechauns and paved the way for other smaller actors to succeed in Hollywood.
Although he endured hard times, brother Jonathan said he would only take on the right roles in productions and movies – grittier characters with more emotional depth.
He said: “Dwarf roles have always been typically exploitative. Peter was the guy who knocked that down forever, he was a trailblazer.”
Their dad John, a violinist, passed away from cancer early on in his son’s career, but not before he got the chance to tell him how “incredibly proud” he was of his achievements.
Recalling the moment his mum found out Peter had been cast in Games of Thrones, she said: “Peter didn’t even have to audition, he was the first one they cast.
“It’s so well-written. I know the torture scenes aren’t real, but I have to leave the room when they’re on.”
But fame has not been easy for Peter, who has two young children with his wife, theatre director Erica Schmidt.
They choose to raise their children out of the limelight, dividing their time between New York and rural Ireland.
His mum said he “doesn’t like fame at all” but attracts adoration wherever he goes.
“Peter says he doesn’t want to be the poster boy for every small person in the world, but he is.”