The Doctor was intrigued by the wonder in this human girl's eyes- whenever she saw something that completely fascinated her, they'd get as big as saucers and brighter than any star in all of space.
Amused, the only thing he could do was watch as she circled the middle console of the TARDIS, her head twisting and turning as she took in the many beautiful colors and sounds around her.
One word she said for an entire hour was 'Wow'.