The composition feels really cramped. Your pixel work is nice for the most part, but I feel like everything is too crowded together, and that there's really no clear focal area.
As Gil pointed out, there are anatomy issues, and I realize that this is a cartoony style, but even with cartoons comes a certain knowledge of anatomy.
I think you'd benefit by widening the canvas and giving more insight as to what the Goblin is doing...it looks as if he's waving, but what's he waving at? What's the story here? Use your visual elements to tell us that.
Lizzrd also makes a point about the jetpack- if it was already firing up like that, wouldn't he be somewhat off the ground? Either way, keep it up- I look forward to your updates. I think you can make this piece very good with the right tweaks.
