Ozzy Osbourne's outspoken wife went public with her sex confession during the season premiere of her American chat show The Talk on Monday (09Sep13), when she opened up about her little-known affair with Leno before she dated and then married the Black Sabbath frontman.
She explained, "When I was 25, I'd just moved to America, I didn't know many people... I had met my husband, but we weren't together... I didn't have a boyfriend because I wasn't very dateable... My friend worked at this place and she said, 'You have to come down to this (comedy) club where I work because it's full of men, you've got to come down.'
"So I've gone down to this club and it is full of men performing and this one person, I think, 'Oh, he's very nice, very funny', so I said to my friend, 'I like him, he's very funny', and she goes, 'I've got his number'. So I said, 'Right, we are gonna prank phone call him!'"
The girls called Leno's number multiple times for a laugh, but Osbourne continued to joke around with the young funnyman and they eventually decided to meet up: "One thing led to another and he actually came to my house and met me and then we had a little fling."
However, it quickly became clear the relationship was just a passing romance for Leno because he soon introduced Osbourne to his future wife.
She recalled, "A couple of months later, he brought around the love of his life for me to meet and she was lovely... and they were so kind to me and we've continued our friendship over the years."
The big reveal came as a shock to Osbourne's co-hosts, Julie Chen, Aisha Tyler, Sara Gilbert and Sheryl Underwood.
She added, "I don't know why I've never discussed it before or shared it or anything, and it's not like it's a dirty little secret..."