Britain's Got Talent supremo Simon Cowell said teaming up with David Walliams for the new series was like having another child to deal with.
Cowell, whose son Eric was born on Valentine's Day, said fellow judge Walliams has "really got annoying this year".
He said: " He was kind of amusing before but God forbid I make the audience laugh more than he does - he gets quite dark."
Asked if the pair get on, Cowell said: " Seriously, I was thinking about it when I was working with him. It's like having a child who's suddenly turned into a giant at the age of 11; he is honestly mentally an 11-year-old in this huge body. He has got a kind side but he can be very, very annoying to work with."
Cowell tipped a group of " incredible motorbike stunt riders" to do well in this series, saying: " I'm amazed that half of them didn't get killed. Love them. They're like modern day Evel Knievels."
But he was less than impressed with another animal act that attempted to recreate the success of 2012 winners Ashleigh and Pudsey.
He said: " We also found a dancing owl that didn't dance, so no fear of that winning. The one I'm dreading winning is a fashion designer, who in my opinion is the worst fashion designer of all time - and somehow he's made it through because David, Amanda and Alesha are on the judging panel.
"I swear to God I don't know what they're seeing because I'm seeing something very different."