Shawn Mendes invited former One Direction singer Niall Horan to join him for a surprise duet of Horan's debut solo single ...

On Saturday, Aug. 16, Shawn Mendes surprised the audience at his show in London when he brought out Horan to duet the former ...

If the whole world were watching, Niall Horan and Shawn Mendes would still make surprise appearances at each other's concerts ...