In the words of Dannii Minogue, Diva Fever had to "forget about the fever and bring on the diva" after illness hit the group this week.
Joe from the duo had to get over laryngitis, but he was fighting fit as they performed a high-energy version of Barbra Streisand, the Duck Sauce hit that samples Boney M.
Judge Louis Walsh told them: "It was like a big, big disco in Blackpool."
Dannii Minogue said: "That song is on my Christmas party playlist. I'm normally getting serious about all this singing and the critiques, but I really like you guys."
Cheryl Cole added "you do just seem like you're having the time of your life up there", while Simon Cowell told them they brought fun to the show.
Rebecca Ferguson put in an amazing performance of Nina Simone's Feeling Good which blew the judges away.
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Louis told the young mum from Liverpool: "What a transformation in one week... You've got so much star quality and I can see you going all the way in this competition."
Dannii said: "In a way that song was a risk because it could become a cliche. But you made it so new. For me I started to think if there was a new Bond soundtrack that would be on it."
Simon told her: "I absolutely love you. You've got it just right. Your timing is perfect, You're very cool, you're very current. Liverpool may have just found itself a new pop star."
It was not such a good night for Blackpool teenager Aiden Grimshaw who struggled with his version of John Lennon's Jealous Guy.
Cheryl told him: "That performance was shaky. I think you've got potential. I'd like to see you do something a little more versatile."
Simon added: "Your face said it all. There were too many times in that song when things went out of control."
His mentor Dannii made a plea for her boy, saying "I hope everybody votes for you because you are a true artist", but a disappointed Aiden said he thought his own performance was "a bit rubbish".
