Well, for flash making in *general*, I'd try to avoid using internet meme. Or at least, making them such a central part of things.
Though since this was for a collab of "what the fuck boom", then that part can be excused... at least, for this.
The art style is okay, but nothing all that great. Not much animation going on besides raising one's arm and swapping for a finger briefly. I'd try to study drawing with structure and just practice drawing in general to get better.
Also, your background is essentially just a green block. Could at least make it look like grass in the background, maybe a bit of shading here and there.
Explosion could be animated and would look better than a tween'ed, badly vectorized explosion. I know there's some explosion tutorials in the newgrounds tutorials, could have a look there.
It's hard to judge just what it is you know and don't with such a small, virtually un-animated example.