Ok, first of all, the glaringly obvious with this is that you blatantly stole TwistedGrim's demon design. From the lack of a mouth, to the black, muscular build with horns and red pupil-less eyes, there are too many similarities for it to be just a coincidence. Even if the design inspired you or Grim's work as a whole did, you can't just plagiarize someone else's work because it looks nice.
Apart from that, there isn't really much to say, it's a trailer, but from what i can see, it has it's pros and cons. The colours are nice and simple, they get the job done right, but the line work is very unpolished. With Flash, you have to constantly fiddle with brush settings and the lines, themselves, to get the lines you want. In this case, they just look like default flash lines, i'm sorry to say.
As for the comedy, i didn't get it, but as i said, it's only a trailer so i can't criticize in that aspect just yet.
The biggest problem i have with this was the cheekiness of stealing someone else's work and claiming it as original, i'm sorry, that is just inexcusable. Try drafting your own character design in a similar vein, just not directly tracing from that design. I hope this review helped give you some insight, and please don't plagiarize art, it doesnt look good on you, my friend.
Not bad. I can't wait for more.