The Carlow native, who's up for a Best Actress award at the IFTAs tomorrow, said she was entranced by leading dancer Jean Butler.
"I wasn't really keen on Irish dancing itself, but I really wanted to be Jean Butler from Riverdance, who danced with Michael Flatley," she said.
"For years she was the person I was going to become when I was older. That's what I wanted to do. They were mystical, mystical people."
The Oscar-nominee also proved she's up for a laugh after filming a cameo role in the new Muppets movie, where she has to ballet dance in the segment filmed in Ireland.
"I was asked to do it. It was one of those things where I was like, 'What? That's ridiculous. The Muppets don't want me to be in their film.'
"But they did and it was amazing.
"I just went in the day before and tried on some tutus and met with the choreographer and we went through some basic ballet moves. I improvised. I just went with it."
Currently filming Brooklyn in Enniscorthy, Saoirse spoke of her excitement about the movie, which co-stars Domhnall Gleeson and features a strong Irish cast.
Based on a novel by Colm Toibin, it tells the story of an Irish immigrant Eilis who is forced to take the steamer from Liverpool to New York in search of a better life.
"It has become a very special film all of a sudden for everyone involved," she said.
"It's almost an all Irish cast and John Crowley is directing it. Julie Walters is in it, Nick Hornby wrote the script, so I'm very excited."