"Some are going to hate it, some are going to love it -- that's a good place to be. It's better than being boring," he said Tuesday night as the finalists slogged it out to get through to the next level.
"I think it was the standout performance of the night...You look interesting. It's almost like you're going to have to now scream at the end of every song. But it kind of worked."
Siobhan took the stage in a completely different outfit than her previous appearances with a different hairdo and combat boots.
The other judges were just as bowled over.
New judge Ellen DeGeneres said she loved Siobhan's new look.
"I love the way you look, I love the way you sound," she said.
Kara said she was having "flashbacks of Adam Lambert. It was the standout performance of the night."