Hillary Clinton made a surprise appearance as Katy Perry was honoured with a Unicef award at the charity's Snowflake Ball in New York.
Clinton, who lost the recent US election to Donald Trump, presented Perry with the Audrey Hepburn Humanitarian Award for her charitable efforts with the organisation.
After receiving a standing ovation herself, Clinton described the Roar singer as someone who has "the spirit and the energy and the compassion that Audrey Hepburn brought to her work from Unicef".
She added that Perry had the most Twitter followers, then jokingly added that she "might have some competition" -- an apparent reference to the ever-tweeting president-elect.
Clinton also said Perry's lyrics "remind us when you get knocked down to get back up" -- causing more cheers to erupt in the audience.
Perry was a big supporter of the Democrat, who won the popular vote, and even campaigned for her. She broke into tears when Clinton surprised her with her appearance at the event.
In her acceptance speech, Perry credited Clinton for helping use her voice for more than just her hits.
"Hillary has lit that voice inside of me, and that light will never go out!" she shouted.
"It will get brighter and brighter and brighter. Thank you, Hillary. You motivate me and so many millions of people who appreciate you for your incredible work."
Perry attended the event without the diamond on her left ring finger which she was photographed wearing on Monday. The pictures sparked rumours of a possible engagement to actor Orlando Bloom.
Clinton has made only one other public appearance at an event since conceding the race to Trump.