Simon Cowell's dogs only walk on their hind legs at home.

The 'X Factor' boss - who has five-year-old son Eric with girlfriend Lauren Silverman - has impressed his friends with the training he's done with his beloved pooches and 'America's Got Talent' star Howie Mandel joked visiting the music mogul is like going to the circus.

Asked about Simon's hidden talent, he told PeopleTV's 'Reality Check': ''Simon's hidden talent is - he would if he could and was allowed to, train dogs. He's got his dogs, and he's trained them.

''When you go to his house, they do flips. They only walk on their hind legs all through the house. It's like a circus! Simon's Circus!''

Despite Simon's 'Mr. Nasty' reputation, Howie insisted his 59-year-old pal is the ''kindest'' person he's ever met.

He said: ''Here's what I will tell you, he is probably the kindest person I've ever met.

''Even though he's reputation preceded him, he was asked to do that, he came to television as an executive but - never on camera - he goes up and really talks, makes sure nobody leaves that stage uncomfortable.''

Simon is devoted to his dogs and in December, he adopted a terrier cross named Daisy while in Barbados, a new companion for his Yorkshire terriers Squiddly and Diddly, and Freddy, his mother's dog which he took on after her passing in 2015.

Simon has previously admitted he plans to ''clone'' his dogs one day.

He said: ''I am 100 per cent cloning the dogs, all of them. We've thoroughly looked into it, got all the details and I can prove to you I'm going to clone them. There is documentation.

''I am doing it because I cannot bear the thought of them not being around. I might actually do it sooner rather than later, which will mean we have six dogs running around.''

Cloning dogs involves taking a DNA swab, and although it's completely harmless to the animal, his wallet won't be so happy as the procedure costs around £60,000 per pooch.

Simon added: ''You hope they're going to be the same dogs and that you'll love them as much as the current ones. I cannot imagine Squiddly, Diddly and Freddy not being around, so this is the solution.''