The 64-year-old producer took part in the first episode of the show’s last series – even making a grand entrance via a rocket ship onto the stage.
However, some viewers were left concerned about his appearance – with some asking if it was ‘definitely Simon Cowell’.
After a previous episode of Saturday Night Takeaway, when the presenting duo made a joke about him having a ‘new face’, Simon denied that he had ever had a facelift.
He told the Mirror: “I think it’s hysterical. I mean, it just makes me laugh. I haven’t had a facelift or anything.
“I’ve had a bit of Botox or whatever, but nothing drastic.
“So when I hear about this stuff, honestly it does make me laugh.”
ITV.
Even fellow guest Stephen Merchant couldn’t help but comment on Simon’s appearance, as he said: “I didn’t like it… I loved it.
“That was my impression of Simon, it wasn’t very convincing because my face moved.”
Ouch.
Fans on X (formerly Twitter) were quick to share their opinion online, with one asking: “Is that definitely Simon Cowell?”
Another claimed he looked ‘more and more like a cartoon every time I see him’.
A third added: “Not sure Simon Cowell has aged gracefully!”
Viewers were also quick to pick up on Merchant’s dig at Simon, with one saying: “Stephen Merchant just proper mugged off Simon Cowell then.”
LADbible has contacted Cowell’s reps for comment.
Ant and Dec had travelled all the way to Los Angeles to pull off the under-cover prank on their long-time industry friend.
ITV.
And this wasn’t the first time he’s been victim to one of their pranks – as he was also their first-ever target back in the day.
Ant said: “It was even sweeter getting him the second time round because we also got him during his downtime as he’s riding his bike around Malibu, it’s very, very funny.
‘We are ending the Undercovers where we started… with Simon Cowell!
“Our first ever Undercover was on Simon in LA when he was a judge on American Idol.
‘So we’ve gone back and got Simon Cowell again.
“We went out to LA and gave him the day from hell whilst he was judging on America’s Got Talent.”