And during school he would take off the voices of Miss Piggy and Kermit.
Now, 24 years later, Stephen can delight in starring in Avenue Q, the Broadway award-winning puppet musical theatre show, the coming-of-age tale which satirises the issues and anxieties associated with entering adulthood.
It's a show that's stormed the world since its first performance 11 years ago.
And when Motherwell-born actor Stephen saw it in London a few years ago, he too was amazed.
"I found it really fantastic," he says.
"And I was taken aback by the skill of the performers, who were bringing these puppets to life.
"And what was especially incredible was that two people were sometimes working the same puppet. Now, that's tricky.
"But as a result I said to my agent: 'You really need to get me seen for a part in that.'
"I badly wanted to learn how to operate these puppets and do their voices.
"I wanted to be part of a show that brings such incredible joy to an audience."
Stephen, who plays three different puppets on stage and has to voice each of them, grew up performing, often revealing his Mrs Doubtfire to friends and family. A career in showbiz was inevitable. Almost.
He said: "I did have a career plan at one time to join the RAF. I loved the idea of being a pilot I guess, although looking back I think my parents wanted it more than me.
"And I went for RAF interviews. But at the same time I really wanted to try acting, and I went to Motherwell College for a year."
Stephen was soon addicted to greasepaint and the notion of joining the RAF flew right out of the window.
"I had discovered theatre and realised that's where my future lay," he says. "So when I left college, I went off to work for a few years, on the cruise ships, singing and dancing.
"Dancing at sea can be tricky. Sometimes you jump up and you find the stage coming up to meet you."
Stephen's work experience was fantastic. He worked on everything from1920s-style shows to singing rock songs.
He got to see the world.
But he felt he didn't have the skill set and the knowledge needed to take him forward.
The answer? He applied to Glasgow's RSAMD, and went back to studying.
"It was great," he remembers.
"I already knew how to sing, dance and make noise.
"But I learned more about real acting, how to make something with meaning really happen.
"I learned how to come at text from an acting point of view, how to refine my technique.
"And it helped. When I left I felt like I was wearing new shoes and I wanted the world to see them."
Stephen, now 31, has appeared in a range of productions, from the Prince in Sleeping Beauty to Anthony in Sweeney Todd and even a show called Zombie Musical.
THE RSAMD taught me how to realise your skills, whether performing or choreographing," he says.
"But I love the range of work I've managed to do, from playing Snoopy in Charlie Brown to Shakespeare."
Stephen, who has two younger sisters, says he handles the down time well.
"I just trust the process. I accept there will be quiet times but I'm confident enough to know that work will come along."
His current dream role?
"I'd love to play the lead in the Book of Mormon. It's a funny show, and the show gets such a brilliant reception.
"And perhaps Les Mis, when I'm a bit older. I just love the challenge of what's out there.!
Stephen did live in Knightswood. But he smiles as he admits he's currently homeless.
"I gave up my flat to do this show and tour the country," he says. "So at the moment I don't really live anywhere.
"But I'm sure that won't be a problem in Glasgow, with friends and family here. And I'll be flat hunting this week."
He's certainly come a long way since the cruise ships. He offers a slice of life on the ocean wave.
"But because you were sharing just four washing machines with a crew of 900 people, you had to wash stuff during the performances.
"So I'd be up there singing a Robbie Williams song, looking out at an applauding audience and really enjoying the moment.
"But then the thought would come into my head; 'I need to get off here fast - and get my underpants out of the dryer."
l Avenue Q, Pavilion Theatre, until Wednesday. Suggested age, over 14.