While I was in bed last night with my Pitbull, she had her head up near my face. My nose was simply exhaling air near her ear, which caused it to repeatedly twitch. If I exhaled more air, it would keep twitching, to the point where she would move her head. I've noticed this back when I used to live with cats as well. The same thing would occur with them.
Why do dog/cat ears twitch when air passed over them? Do they have some sort of reflect or are they just more sensitive? I will say that when I am exhaling at a normal rate, the air flow isn't that fast. I can understand that it may be more annoying when I purposely exhale faster.