The music mogul, who created the talent show, posed alongside lead actor Nigel Harman and the musical's writer Harry Hill at a London photocall on Monday (2 September).
Simon tweeted on 2 September: "Very excited to attend the press launch of The X Factor musical @icantsingUK today, as usual I got it completely in the neck! But I love it."
Former EastEnders star Nigel plays Simon in the production, which focuses on a girl called Chenice who has never seen X Factor before but ends up auditioning.
It's been promised the musical will be a "lid-lifting theatrical rollercoaster ride behind the scenes at the mother of all singing competitions".
Chenice is played by Cynthia Erivo (currently on stage in The Color Purple, while Holby City's Alan Morrissey will star as another contestant, described as a "plumber/environmental warrior".
Simon said yesterday he isn't concerned about how Nigel plays him on screen or if the musical pokes fun at his talent show baby.
"I didn't want to do a musical we took too seriously - it's a fun show. The big thing for me was if the songs were good or not, but I get it in the neck throughout," he said. "I never thought the musical would materialise and when I went to the workshop I was laughing so much I thought, 'we've got to make this show'."
Yesterday, it was hinted the script of the show might be altered slightly to take account of Simon's recent baby news. The 53-year-old has confirmed he is expecting his first child with New York socialite Lauren Silverman.
This week, the father-to-be gushed about seeing his baby for the first time via a scan, telling The Times: "It is just surreal. You see this thing which is now alive moving around. I feel very paternal right now. So I am very happy."
Simon jetted into the UK with Lauren last week ahead of The X Factor launching its tenth series. The show - featuring judges Gary Barlow, Nicole Scherzinger, Sharon Osbourne and Louis Walsh - premiered on ITV over the weekend, drawing huge viewing figures.
The X Factor musical opens at the London Palladium on 26 March. Previews start from 27 February.
X Factor's winners through the years in pictures:
Copyright: WENN Harsha Gopal