At first, what with the sudden stiffness (don't think improper thoughts Tails don't think improper thoughts she won't know how to react) and the following slight tearing up and practically glowing blush... and he looks down, sheepishly.
"C...Cosmo? I didn't... I mean, you... I... I didn't mean to upset you, if that's what I... I mean..." One kiss was really all it took. He was right back to the stammering, sheepish little kid he was ten years ago, just in a more grown-up body.