Pink sings with the public in London's Trafalgar Square
Do you remember the T-mobile advert where most people in a London train station started dancing and singing, well the mobile phone network has been at it again...
They recorded thousands singing karaoke in London's Trafalgar Square, but the crowd were in for a surprise as US singer Pink turned up and sang along with them.
She was cuddled and kissed as fans crowded around her and went crazy.
Adverts have come a long way. As thousands of people poured into Trafalgar Square on Thursday night, you'd be forgiven for thinking it was simply some sort of concert.
But these people hadn't shown up to see anyone in particular - they were there to be a part of the latest viral ad campaign for a mobile phone.
You probably saw the last one this company put out: it involved a lot of dancers breaking into action at Liverpool Street Station.
It has now been seen by more than 11 million people on YouTube, as well as millions more on TV.
Pink shocked thousands of volunteers after making a surprise appearance at the filming of a TV commercial in Trafalgar Square.
The crowds were being filmed singing songs by Britney Spears and The Beatles when the star made her presence known to the public.
An image of the popstar was transmitted over giant screens before she appeared on a stage halfway through a rendition of Emma Franklin's 'Piece Of My Heart'. She then removed her hood and sang her number one single 'So What'.
Speaking to reporters after the event, she said: "What a fantastic experience! Everyone singing along together in the middle of London - it was incredible.
"I was thrilled to be a part of such an amazing event and to share it with so many people."
Pink plays London's O2 arena on May 1, 2 and 4.