Tails' reaction to girls throughout the story. He's not very good at interacting with them when the subject of romance comes up.
In Chapter 026, Tails insists he flies down to the Undercity with Carth. Carth thinks Tails has gone soft in the head, so Tails demonstrates... by jumping out the window of an air shaft. When Tails reveals, with Sonic-like smugness, that yes he CAN fly, Carth punches him square on the nose!
Tails: "OK... maybe I deserved that..."
Carth: "Damn right, you did!"
After his nightmare in Chapter 040, Tails wakes up to find someone snuggled up against him. With building panic and horror, Tails slowly turns his head, tracing his eyes up the interloper's arm, until he's face-to-face with Mission Vao. His blood-curdling (if entirely mental) scream is what sells it.