Ruby Isaac was invited on stage by the Hollyoaks actor in front of a packed market place after she had interviewed him - he had refused to take to the stage without the youngster.
Latimer Arts College student Ruby had quizzed him for her You Tube channel 'Ruby Tube' after which Mr Mellor generously invited her to join him to perform the switch on with Mayor of
Kettering Keli Watts and CBBC star Ed Petrie.
She said:"It was pretty scary. Switching on the lights was amazing."
Will Mellor said: "It's been great. All the community has turned out and we've got into the festive spirit. I love family and I love community - this is both and everyone has been so friendly.
"We even had an impromtu sing-song so it's been great."