Ryan Gosling surprised Barbie director Greta Gerwig yesterday (August 4) with a flash mob to celebrate her 40th birthday.A video was posted of the flash mob to Barbie‘s official social media channels. Gerwig was in a pilates class when a group of dancers arrived and performed a routine set to Gosling’s song from the movie, ‘I’m Just Ken’.Gerwig is seen tearing up as the dancers perform before hugging them after the dance ends.“As Kens know…. Sometimes the only way to express your feelings is through song & dance,” was the accompanying caption on the video.