The 'So Macho' singer drops in on the show's audition tour to pay a visit to her close friend and former mentor - leaving David Walliams, who famously refers to him as 'my Simon', a little green with envy.
"This is Sinitta Simon, I don’t know if you’ve met," quips the comedian.
"This is my Simon, by the way," she warns. "Not your Simon, my Simon. Mine."
Always one to relish being the centre of attention, Simon watches on as the rivals begin squabbling over who should take his coat.
"No, Simon actually likes it if I take his coat," insists David.
Sinitta then offers Simon a cup of tea, with David retorting: "He likes it how I make it. He doesn’t like it the way you make it."
But it soon becomes clear who the media mogul favours when he tells Sinitta that she can sit near him, but not next to him.
"Why is David? I bet David is sitting next to you?" she wails.
"No, David is as far away as possible," Simon smiles.
Flick through snaps of the exchange below, and tune in to ITV tonight at 7.00pm to see Sinitta's cameo in full...