Something about the 'tall' comment gets under his skin, and he makes a face at him for it.

"Look, lesson one with this outer-space mumbo-jumbo life, don't expect things anymore! Everything's random! You'll think life will start to make sense again for a while and then, bam— a new kind of crazy!"

He flails his own hands around in response. This is all a sore, sore spot, time-stuff. He needs a second to adjust. He doesn't know how to handle this. Sorry he's just... mouthy, Aang. This is his moment of a 'new kind of crazy.'