Pop star Britney Spears is set to make a special appearance at Madonna's world tour, which kicks off next month.
But concert goers won't see Britney in person, because she will be appearing in a video, which will be shown as part of Madonna's show.
A spokeswoman for the queen of pop said Britney was doing some filming - but wouldn't give away any more details.
She said: "There is footage being shot of Britney Spears some time this week - the rest is 'a secret'."
Madonna kicks off her Sticky & Sweet tour on 23 August in Cardiff and will perform at the Wembley Stadium in London in September.
She'll then travel through Europe, before taking her show to America.