LONDON, UK - Viewers and judges on Britain's Got Talent were perplexed on Friday night when Irish schoolboy magician Cillian O'Connor vanished during his performance in the live semi-final.

Cillian, who has Autism, took the stage and millions of viewers' screens for the final live semi-final and again used judge Simon Cowell as part of his act.

Cillian requested that Simon write a random word on a handkerchief with his initials to make it unique. Simon wrote the word 'dog' on the hanky and placed it on the judges' table before him.

Meanwhile, Cillian requested that Judge Bruno Tonioli bore a hole through the center of an apple before requesting that the Italian wrap it in a cloth and hold it above his head.

Cillian then displayed Simon's handkerchief to the audience before making it vanish before their eyes. He then unwrapped the apple, which now contained a hanky.

When Simon pulled it out, it was revealed to be his one-of-a-kind creation. The audience gasped, and Simon sat open-mouthed as the 13-year-old made his way to the stage for a big finish.

He appeared to throw the handkerchief into the audience while standing in the center of the stage. As an animated version made its way around the studio and back to the stage, it erupted in a confetti shower. Cillian was no longer on stage when it settled.

He reappeared moments later from a cardboard box placed on the stage to a standing ovation from the judges and the audience.

"I'm at a loss for words," Judge Amanda Holden said, while Simon said, "there's just something about you." The difficult-to-please judge stated that he still believes in magic and added, "so do they," as he pointed to the audience members who remained on their feet.

"You're so good at what you do," Simon added before Bruno declared, "we're all spellbound."

Home viewers were equally impressed and took to social media to express their feelings.

Only two acts from Friday's semi-final will advance to the grand final on Sunday night.