Shawn Mendes brought out Niall Horan at his show in London for a surprise duet of "This Town." "I'll remember this for a long ...

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

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