omg if that happend i would totaly go up to sing with him and put one arm around him while singing but try to keep calm and sing the best you can omg and then after the show he'll ask me o go with him to the backstage and i'll get his autograph and post it on the internet and kiss him in the cheek ahhhhh......... lol :D

i would come on stage and sing with him and after the concert is over kiss him on the cheek and thank him for a wonderful time and i would exchange numbers

I would go up and modestly say that I'm not a very good singer (which is true) and he'll say thats ok just sing your best. And I will. And hopefully he might ask me back stage afterwards or give me something of his.:)

I would totally go up there and sing with him. Then later hang out with him and kiss him on the cheek. Ask him for his phone number and tell him lets never forget each other. WHAT A FANTASY!!!! :) HAHA!

OMIGOSH! *sigh, SCREEAAM! I would so wayyy go up and sing with him. HELL YES!!

I WULD SO GO UP AND SING WITH HIM AND IT WOULD BE LIKE A DREAM COME TRUE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!