"Saturday Night Live" alum Jimmy Fallon returned as guest host this weekend and, along with musician Harry Styles, led a flash mob to dance to the late David Bowie's hit song "Let's Dance."

"It's so great to be back here on 'Saturday Night Live.' This is where it all started for me. I'm really so happy to come home," Fallon said during his opening monologue.

"Tonight is extra special because this is the first time in 'SNL' history that we are going out live coast to coast all across the country and Canada. ... Tonight is bigger than a show. It's a party!"

As "Let's Dance" began to play, he urged those sitting in chairs in front of him to follow him down the hall and throughout the building, picking up random people along the way, including Styles.

The stunt ended with Fallon and his followers joining the regular 'SNL' cast members on the show's main stage.