Ok well originally I wasn't going to comment because I assumed it was just a preliminary Maya animation test (as it is), and that you weren't worried about getting the animation down too well....but you asked for it
-The opening pose....I like what you're doing with the tongue etc...but you need to exaggerate it a bit more. I'd say tilt his head over to the right...have one eye closed a bit more than the other etc. Right now it's not reading right and I honestly had no idea what he was doing, the first time I watched it
-The 2nd pose (where he takes a break between reaches, and lets his arms down momentarily) looks awkward....he has his hands out like he going to exclaim something, as opposed to getting ready to reach back again. I'd say have him let his arms down to his sides as if he's trying to catch his breath or something (because he is working quite hard at it

)...might need to stretch that area of the animation out a bit more (maybe even have him wipe his brow or something)...but right now it's still not reading right.
-The 3rd pose (where he reaches back again)...looks great! Very natural
-As another thing...when he is reaching back...there doesn't seem to be any detailed hand/finger motion...it just looks like he drapes his hands over his back and waits

....maybe have his fingers move around as he is struggling to grasp onto something (the crazier the finger/hand motion, the better)
-When he says "could be worse", the timing on his right (our left) arm is a bit off. It snaps back at "could be" when it should only snap back at "worse"
-Same thing with the timing on his eyes. He looks up at "could be", when he should only be looking up at "worse" (because of the intonations in his voice).
-When he says "worse", try having his mouth open a little less (open as in, to pronounce the "orse"...right now that part looks a little odd).
Other than that...nice job

Very smooth posal transitions etc...looking forward to seeing this done!