Australian actor Rebel Wilson says her surprise performance with rock band The Kooks at a British music festival was planned half a day in advance.

Wilson, 45, best known for Pitch Perfect, joined the rock band on the main stage during their Friday set at the Reading Festival, where she sang a rendition of Coolio’s Gangsta’s Paradise.

The performance went viral.

“The Kooks are super popular in Australia, where I’m from, and they said they were open to a collab. Because we only worked this out 12 hours in advance, I didn’t want to butcher one of their songs… so I suggested we do Gangsta’s Paradise,” Wilson said.

“The boys were really into it, so we whipped up a rendition over the night. The fellas are so great. It was so fun.”

After Friday’s performance, the band shared a video on Instagram and said: “Joined by the incomparable @rebelwilson to perform one of our favourites. Truly unforgettable, thank you @officialrandl.”

The Brighton-formed band are fronted by Luke Pritchard with Hugh Harris on guitar and Alexis Nunez on drums.

The Kooks released their debut album, Inside In/Inside Out, in 2006, which reached number two on the UK chart.

It was followed by 2008’s Konk, which became the group’s first number one album in the UK.

—AAP