FUCKING AMAZING!!!! I really like the patterns in the background and the subtle inclusion of color. The color scheme is very simple--just red and blue--but the effect to that end is actually really cool. And the fact that the guy's wearing glasses, a bandana, and has dreadlocks just makes me think he's REALLY high... which isn't helped by the fact that he's drooling.
I like how inconsistent the linework is, too; I normally do that to a lot of my work (i.e. varying thickness and such). It's really something I use to emulate depth or even just make my pieces look cooler, and I think you used the technique very well. The only suggestion I have to give--because your style is actually really good--is perhaps make the lines a bit more defined around the guy as you did the pandas. There is a level of inconsistency that isn't constructive, and I'd say that would be the difference between the thick-lined pandas and the thin lines around the guy's face. Just emphasize on the guy a little; maybe darken some major areas like the outline of his jaw, his bandana, his shirt, hair, glasses, etc. Fine lines are good, but there should also be a bit of a contrast to make it looks consistent with the pandas.
Also, try to make the "panda!" in his mouth white and his mouth black, or even red. That might work out better. You also seemed to add some shading a bit to the face--expand on that.
I don't know about the little alterations; really, they're not even necessary because this is still fucking amazing. I just think they would add a little bit more.