13-year-old Sydney Bourbeau was singing "Thinking Out Loud" for a fundraiser for the Local Human Society. She was at the Canadian West Edmonton Mall where unknowingly Ed Sheeran was in a music store nearby. He heard her and then went up on stage to join her in a duet. Coolest experience ever!
Many people have noted that she seems extremely calm for meeting a celebrity unexpectedly in the video. But the thing was she had no idea it was Sheeran at first glance. She thought someone was fixing her mic and then when she realized it was Sheeran, she wasn't sure what to do. It's impressive that she remained good composure and kept going!
“I was like, should I stop? I didn’t want to stop, but I wanted to talk to him,” Bourbeau told the newspaper. “This is, like, the best thing that’s ever happened to me.” - Edmonton Journal
But telling from her tweet, she was thrilled that it happened.