It seemed like an intriguing request, thought Goo Goo Dolls founder John Rzeznik at the time. And one that was impossible for any kind-hearted rocker to resist. Looking out into the crowd as the band’s set built to its signature smash “Iris” — the 1998 single that spent 18 consecutive weeks at #1 on the charts that year —he saw a young girl, standing with her father, holding a placard that earnestly read, “I want to come up and sing ‘Iris’ with you.’ The novelty of it intrigued the vocalist/guitarist — was this kid really a fan? Did she have what it takes to go head to head with his trademark