The 15-strong group, who are all aged between 66 and 88, performed their unique take on the Beastie Boys' (You Gotta) Fight for Your Right (to Party!).
Their oldest member, Londoner Grace Cooke, impressed Cowell, who told her: "You on the right, you're a little tiger aren't you?"
Less impressive were Twisted Disco, a dance troupe from York, who were dismissed by Cowell as being "like eight Jodie Marshes on a normal day out shopping."
Also on the ITV1 talent show was violinist Analiza Ching, from Beaconsfield, Enfield student Richard Bolongi and 16-year-old Ashleigh Butler, from Northampton, and her dancing dog, Pudsey.
Another act to impress the judges was Chelsea Redfern, whose version of Prince's Purple Rain leaves David Walliams predicting she could be a "superstar."
Cowell told the 18-year-old office worker from Chesterfield, who made it to the bootcamp stage in last year's X Factor, that "not only do you sound like a pop star, you look like a pop star."
And one of the most popular comedy contestants of the night was Mr Zip. The 49-year-old plasterer from Manchester won over the hearts of the audience with an impersonation of Prince Charles before diving into his self-written song Lost My Keys, Lost My Phone.
A bemused-looking Cowell admitted: "When you started I thought you were annoying, then you got more annoying, and then I liked you."