We first met Rob at try outs for BGT's 13th series earlier this year.
Amanda Holden, Alesha Dixon, David Walliams and Simon Cowell were back in their usual spots behind the judges' desk with Ant and Dec watching on from the sidelines as always.
28-year-old Rob King from Manchester walked out on stage, revealing he worked at the very theatre where auditions were being filmed.
"I think my boss is somewhere up there," he quipped.
Rob performed Conchita Wurst's Rise Like A Phoenix to get four yeses from the judges.
Following his performance, Rob revealed the emotional reason why he decided to audition.
Rob told the Daily Mirror how he had been inspired to sing for the judges following the tragic death of his friend Martyn Hett in the Manchester Arena attack.
“Martyn made a huge fuss of each of my pub gigs and used to sit in the front row absolutely screaming each word back at me," Rob explained. “His friendship, and loss, has been a vital life lesson. He never wasted a second and seized every opportunity.
“After he was taken, the hashtag BeMoreMartyn inspired people to be more positive and go-ahead like him. I think of him every day.
“Martyn’s the reason I applied for BGT. He was on my mind as I stood on stage trembling in front of Simon Cowell. He gave me that strength.”
Britain's Got Talent wasn't Rob's first time on TV.
He was recently seen as part of The 100 on BBC One's singing talent show All Together Now.
After making it through his audition, Rob was chosen by the judges as one of this year's live semi-finalists.
He'll sing live tonight, competing for a place in the live shows.
Ron teased: "My next performance is going to be a twist on a familiar song. It's going to be big, dramatic, and a little different."
Britain's Got Talent 2019 airs on ITV from 7:30PM tonight with the results from 9:30PM.