Julia Roberts gave the cast and crew on her new movie knitting tips after she turned up to the set one day and found everyone with needles and wool.
Co-star and director Tom Hanks thought it would be fun to pretend everyone had caught the actress' knitting bug and sent out for needles and skeins of yarn from a nearby knitting store.
He then called on everyone to gather the next morning before Roberts showed up for work and take a quick lesson in knitting so grips, lighting men, extras and runners would all look like they knew what they were doing when his leading lady arrived.
And the prank worked - Roberts shrieked when she saw the cast and crew stitching and purling and offered to give them all tips.
The whole thing was caught on camera and it's being used to promote Hanks and Roberts' new film Larry Crowne.
The actress admits she was thrilled: "You walk into a room and 65 men are knitting; it catches your attention."