A series of videos posted on Instagram on Sunday captures the duo getting the party started. As soon as the Dirty Dancing song starts playing, Harry, 20, and Kristen, 41, can be seen hugging and singing along to the track, delighting onlookers with their impromptu moves.
Both stars are clearly in high spirits, and cannot contain their laughter as they belt out the hit single.
Kristen had earlier made a surprise appearance on the show, interrupting host Amy Adams during the opening in an attempt to "jazz up" proceedings. Harry, meanwhile, appeared on SNL alongside his One Direction bandmates, Niall Horan, Liam Payne, Louis Tomlinson and Zayn Malik.
The boys appeared in a comedy sketch, posing as a squad of high school dancers, before taking to the stage to perform their ballad Night Changes, and single Ready To Run.