Nice idea and the layout is nice too. I think the main things that hurt it are the bold colors and the boxed out bottom. The drawings quite nice and I agree that the thought bubble into the smoke is very cool. When dealing with several hues (Blue shirt, Green and Red background) try to keep the saturation and intensity down a bit. By nature, these 3 colors clash with each other. So having them really bright and bold just screams at you. Red, in particular, should really be used sparingly. Just keep that in mind.
Each entry is a learning experience so keep at it!