Back off and let this kid animate his ninja blob.
Don't chuck him into the deep end, he needs to learn how to animate with a style he's comfortable with.
Spend more time adding inbetweens to smooth the movements out and give the ninja some different poses to show he's alive, rather than cleaning up your art. You can always go back and refine the character after. It's a much easier way of animating than working with fully developed drawings.
Now onto the throw animation...
When you throw something, you don't usually stand still with both feet planted on the ground. Your whole body moves with an action like that.
Practice in front of a mirror by throwing a knife at a wall or something (lol). Watch how your body twists, leans and moves forward as you throw it. You usually step forward in the direction you're throwing it with your opposite leg and your non throwing arm swings backwards.
Once you've understood the action, sketch the main poses out in flash (can even be done as stick figures). Then add the movement in between, and go over it all on a layer above to refine the art and give him a body.
Thats one way of doing it.
Good luck kid.
Practice, practice, practice.
Also, who are you guys to tell him it's not worthy of a thread? Where's your gold aura???
He wants constructive critique and he wants to improve his skill and learn. He's not looking to whore out a random clip he made for praise. Last time I checked it this was a also a flash help forum.