Taylor Swift took to the stage somewhat unexpectedly on Jimmy Fallon's Late Show as the host returned following a week off to mourn his mother's death. It was an unplanned tribute -- producers wanted to do something special for Jimmy on his first night back and since TSwiz was in town to tape Saturday Night Live, she obliged.

Fallon producer Mike DiCenzo Tweeted about it, saying, "First, a quick word about Taylor Swift. She was not scheduled to do our show today. But we wanted something special for this first show back, so we asked her on a complete whim, since she had been in town doing SNL. She said yes with zero hesitation." He went on to write: "She sang ‘New Year’s Day’ No one had heard it. Suddenly she sings the line, ‘Squeeze my hand 3 times in the back of the taxi.’ I nearly gasped. Tears. I think everyone in the audience started sobbing,” he added. “I could see Jimmy silhouetted at his desk dabbing his eyes with a tissue. We all lost it. It was a beautiful coincidence in a beautiful performance. ‘Hold on to your memories, they will hold on to you,’ Taylor sang.

Fallon opened the show with a tribute to his mom who passed on Nov. 4.