Watch Paul McCartney and Dave Grohl Perform 'I Saw Her Standing There'

Paul McCartney reunited with his “Cut Me Some Slack” pal Dave Grohl Saturday night when the Foo Fighters frontman made a surprise appearance onstage at McCartney’s London concert to perform the Beatles classic “I Saw Her Standing There.” While past collaborations between the two rockers have seen Grohl sit behind the drum…