Cast your mind way back to the early X Factor series, and you'll remember when Si was 'Mr Nasty' who thought nothing of totally crushing contestants' hopes and dreams on national TV.
Well thankfully a lot's changed since Simon used scathing put downs like this gem: "If your lifeguard duties were as good as your singing, a lot of people would be drowning." Ouch.
Why has the music mogul got so mellow? We reckon it's down to Simon having his heart melted by the birth of his mini-me son, Eric.
Speaking to the Mail on Sunday's Event magazine about being a dad, Simon said: "This was not something I planned, but I remember going to the first scan with Lauren [Silverman]. I called him Tad because he looked like a tadpole. Something just kicked in. I felt unbelievably protective of both of them. I just absolutely wanted him. I just hadn't known that before."
How cute is that?!
Mum, Dad and Eric. Now two days old. pic.twitter.com/ChWlrXmtmO— Simon Cowell (@SimonCowell) February 16, 2014
Simon also spoke about his surprise at becoming a father, revealing the news came as a complete shock to him.
Lauren was married to Simon's best friend Andrew when news that she was pregnant with Simon's child broke in July 2013. Addressing the situation, he said: "I'm not proud of the circumstances. I can't hold my head up about it. But we have all moved on."
For exclusive competitions and amazing prizes visit Reveal's Facebook page NOW!