His heart had skipped a beat when he saw a Doctor who wasn't the one he'd... got to know here, but by the time he'd got close enough to speak, he could see it wasn't his Doctor. Too relaxed. Far too relaxed.
Still, it was a Doctor. And the right regeneration at that.
He stopped a few feet away, hands in his jacket pockets, raised an amused eyebrow at the bubbles, and said, rather shyly, "Hi."