He was known for being Mr Nasty in his earlier days of being a TV judge.
And after softening somewhat in recent years, Simon Cowell, 58, was reunited with a former Pop Idol contestant that he sent home during auditions 17 years ago.
In scenes that will air on Saturday's episode of X Factor, Simon is left startled as Danny Tetley, 37, serenades him, before apologising for sending the singer home during his Pop Idol days.
X Factor SPOILER: Simon Cowell is set to apologise to Pop Idol contestant Danny Tetley in the music show's premiere episode after rejecting him 17 years ago
Simon did not initially recognise Danny when they came face-to-face on the X Factor, with the singer, first charming Ayda Field by telling her she's 'looking gorgeous', before bonding with Louis Tomlinson over their Yorkshire roots.
Robbie Williams is also taken in by him, explaining: 'I'll tell you what you've brought some personality onto the stage already and thank god for you!'
Asked why at the age of 37 he hasn't worked in the music industry yet, Danny admits: 'I did try for Simon many years ago on a TV show called Pop Idol, not a lot happened, it's why I'm back here.'
Danny then proves his skills have only improved since as he wows the audience with a rendition of Broadway hit And I Am Telling You, pointing directly at a stunned Simon when he belts out 'you're the best man I've ever known'.
New man: He was known for being Mr Nasty in his earlier days of being a TV judge, but Simon has softened somewhat in recent years
Proving himself: Explaining his situation, Danny said: 'This is my World Cup final, I've waited 17 years to show I've still got it, I've still got the same passion as before'
It's not just the public he impresses, as husband-and-wife duo Robbie Williams and Ayda Field stand up to enjoy a slow dance together.
Not only that, but the audience then give him a standing ovation before Simon apologises for saying 'no' 17 years ago.
And Danny proves there's no hard feelings between himself and Simon as he reveals: 'Simon was very nice but back then