A fun little cartoon. I particularly like the way "NOT" comes out of the speech bubble, though I wonder if the exclamation mark should have had a white drop shadow too as it is also come out of the bubble.
Maybe a bit more detail on the shadows would have been nice. I get that it's in a simple cartoon style but I would have liked to have seen some more shape there.
I think the arms could have been higher on the body too. As they are the right arm (viewers right) appears to be coming from his back due to it being behind his underwear, making it seem almost like a tail. I would have but them inline with the center of the mouth, he's a monster, he can rock that look.
I am just pointing out the little things that I picked up on and some of it could be my opinion and how I would have done things. I do think this is a good piece.
