Zuko stares back, his own expression flat and a little grumpy.

Quick as lightning, he reaches out and pokes Hiccup - not in the eye, but right between his eyebrows. Between the force and the speed, it's enough to get Hiccup's attention. And definitely sting a little.

"Lesson one. The only thing you should be staring at is your whole enemy - not how many scars he has."

Otherwise, your enemy has a window into, well, things like that.

It hasn't occurred to Zuko yet that Hiccup might be staring at his other eye.